Celtic Seas

Assessment sheet for Celtic Seas sub-region and for five subdivisions

Celtic Seas

Summary

The physical disturbance pressures from mobile bottom-contacting fishing gears varies spatially in the Celtic Sea sub-region, with 83% of the grid cells (I-2), and 53% of the surface area (I-3) <200m being fished on average per year for the period 2013-2018 (Table 1). Fishing is aggregated with 90% of the pressure occurring in 36% of grid cells (I-4). More intensive fishing occurs in the zone >200m depth in the Celtic Sea.

No longevity layer was available for the Celtic Sea region – declines in community biomass relating to impact cannot, therefore, be calculated for either the L1 or PD method.

Maps of spatial distribution of surface abrasion, economic value and weight of fisheries landings are shown in Figure 1. It is evident from the weight map that there is a mistake in the weights for the region, and weights are not presented in further analyses. The value layer also appears incomplete.

Table 1

Table 1. Pressure and impact indicators for 2013-2018

Indicators	0 to 200 m	200 to 800 m	more than 800 m
Average intensity (I-1)	1.65	2.00	0.03
Proportion of area in fished cells (I-2)	0.83	0.77	0.11
Proportion of area fished per year (I-3)	0.53	0.54	0.02
Smallest prop. of area in fished cells with 90% of fishing effort (I-4)	0.36	0.36	0.02
Proportion of area in unfished cells (I-5)	0.17	0.23	0.89
Average PD impact (I-6)	NA	NA	NA
Average L1 impact (I-6)	NA	NA	NA
Proportion of area with PD impact < 0.2 (I-7)	NA	NA	NA
Proportion of area with L1 impact < 0.2 (I-7)	NA	NA	NA

Figure 1

Figure 1 Geographic distribution of surface abrasion, seabed sensitivity (not shown) and total value and weight from mobile bottom-contacting gear. The maps of surface abrasion, value and weight show the average per year for 2013-2018

Pressure

The distribution of fishing intensity in the Celtic Sea has a strong spatial variation (Figure 2), extending out in the west to the 1000 m. Fishing is mainly concentrated along the shelf edge, i.e. around the shelf and shelf-edge and on fishing grounds in the Irish Sea. Areas with lower intensity occur in parts of the central Irish Sea and in some coastal areas to the west of Ireland.

The proportion of area subject to fishing pressure differs between broad-scale habitats and is highest in offshore circalittoral mud 99% of grid cells fished) and offshore circalittoral sand (93% of grid cells fished) (Table 2). Fishing intensity is highest in offshore circalittoral mud (average intensity = 3.67 year-1) and offshore circalittoral sand (average intensity = 1.91 year-1).

Total fishing intensity is largely unchanged over time (Figure 3). However, there has been an increase in the intensity in upper bathyal sediment since 2016. Fishing intensity is relatively stable over time in circalittoral sand, abyssal areas, and offshore circalittoral coarse sediment. Average trawling intensity is more variable over time than the proportion of area fished (Figure 3, compare left and middle panel), but a single-year reduction was seen in most seafloor categories in 2017. Taken over the 10 year reporting period, this comparison shows that changes in intensity have not affected greatly the spatial distribution of the footprint.

Fishing pressure is aggregated, both at the regional level as well as at the level of the habitat (Figure 3, right panel). In all but abyssal areas, which are subject to a very small fishing footprint, the smallest proportion of habitat with 90% of effort varies between 20-48%. The intensively fished areas represent the ‘core fishing grounds’. These grounds contribute most of the landings and value (Figure 4). Almost 90% of the fishing effort (swept area) and 80% of the landings and value, occur in only 20% of the surface area of the Celtic Sea (Figure 4).

Figure 2

Figure 2 Surface abrasion, Swept Area Ratio, by mobile bottom-contacting gears (year-1), averaged for the 2013-2018 six-year cycle

Table 2

Table 2 Overview of pressure indicators of all mobile bottom-contacting gears per broad-scale habitat averaged for 2013-2018. I refers to the indicators in Table 1.

MSFD broad habitat type	Extent of habitat (1000 km2)	Number of grid cells	Landings 1000 tonnes	Value 106 euro	Swept area 1000 km2	Average intensity (I-1)	Prop. of area in fished grid cells (I-2)	Prop. of area fished per year (I-3)	Smallest prop. of area with 90% of fishing effort (I-4)
Offshore circalittoral coarse sediment	142.40	11795	NA	129.53	252.56	1.77	0.87	0.54	0.26
Offshore circalittoral sand	127.07	11354	NA	91.34	242.12	1.91	0.93	0.73	0.39
Offshore circalittoral mud	64.60	5416	NA	95.00	237.11	3.67	0.99	0.87	0.42
Upper bathyal sediment	156.59	10560	NA	85.04	225.50	1.44	0.59	0.39	0.24
Upper bathyal sediment or Upper bathyal rock and biogenic reef	43.13	2781	NA	10.83	31.36	0.73	0.62	0.23	0.14
Unknown	42.64	5895	NA	8.21	21.04	0.49	0.68	0.25	0.12
Offshore circalittoral mixed sediment	9.41	1788	NA	5.93	9.29	0.99	0.76	0.30	0.17
Offshore circalittoral rock and biogenic reef	6.82	3224	NA	3.33	6.31	0.93	0.79	0.30	0.14
Circalittoral coarse sediment	20.60	3545	NA	7.78	5.62	0.27	0.75	0.17	0.15
Circalittoral sand	11.16	2422	NA	2.38	3.72	0.33	0.65	0.19	0.14
Circalittoral mud	4.82	1231	NA	1.66	3.56	0.74	0.77	0.34	0.17
Circalittoral rock and biogenic reef	9.27	3547	NA	1.45	1.88	0.20	0.57	0.14	0.15
Infralittoral sand	1.96	951	NA	1.55	1.24	0.63	0.52	0.20	0.03
Infralittoral coarse sediment	1.27	944	NA	1.78	0.68	0.54	0.63	0.19	0.04
Circalittoral mixed sediment	0.96	588	NA	0.30	0.34	0.36	0.71	0.25	0.20
Infralittoral rock and biogenic reef	1.96	2159	NA	0.45	0.31	0.16	0.50	0.10	0.11
Lower bathyal sediment	117.09	7970	NA	0.22	0.31	0.00	0.05	0.00	0.03
Upper bathyal rock and biogenic reef	0.82	329	NA	0.15	0.18	0.22	0.24	0.10	0.06
Abyssal	139.78	8092	NA	0.23	0.17	0.00	0.04	0.00	0.02
Lower bathyal sediment or Lower bathyal rock and biogenic reef	33.97	2276	NA	0.18	0.11	0.00	0.14	0.00	0.07
Infralittoral mud	0.40	440	NA	0.10	0.04	0.10	0.36	0.07	0.10
Infralittoral mixed sediment	0.19	238	NA	0.01	0.02	0.11	0.34	0.08	0.10
Lower bathyal rock and biogenic reef	0.48	179	NA	0.00	0.00	0.00	0.01	0.00	0.01

Figure 3

Figure 3. Time series of (a) mean fishing intensity (surface abrasion), (b) proportion of the surface area of the seafloor fished, (c) aggregation of fishing (proportion of the surface area with 90% of the fishing effort) by habitat. Results represent vessels over 15m (2009-2011) and vessels over 12m (2012-2018).

Figure 4

Figure 4. Cumulative proportion of the swept area, landings and value. Grid cells were sorted from highest to lowest fishing intensity and include non-fished cells. The results are for all mobile bottom-contacting gears based on averaged fishing data per c-square from 2013-2018.

Core fishing grounds

Core fishing grounds are defined as the c-squares with the 90% highest value of landings in the VMS data. Figure 5 shows the number of years c-squares are within the 90% highest value by métier. If fishing in a métier occurs in the same c-square every year with high value of landings, the rightmost bar in Figure 5 will be high, meaning that the c-square is within the 90% highest value of landings every year during the period 2013-2018. If a c-square is only within the 90% highest value in one year, it will end up in the bar at the left. Figure 6 shows the percentage area overlap between the 90% highest value per year and the reference fishing ground. Both figures highlight that otter trawling for small pelagic and mixed fish (OT_SPF, OT_MIX) and the seine (SSC_DMF, SDN_DMF) have the highest variation in space.

Figure 7 illustrates the relationship between area fished in percent and the cumulated value of landings, sorted from the c-squares with highest value fisheries. The curves are start steeply, illustrating the concentration of the fisheries at fishing grounds, and their horizontal component illustrate that peripheral fisheries exist outside the main fishing grounds.

Figure 8 shows the area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018.

Figure 5

Figure 5. Number of years c-squares are within the 90% highest value by métier, presented as a % relative to the total number of c-squares (n) that are within the 90% highest value by métier across all years. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 6

Figure 6. Percentage area overlap between the 90% highest value per year and the reference core fishing ground. For métiers that are included in Figure 5 and missing in Figure 6, no reference core ground could be established and/or métiers were not used in the area in some years.

Figure 7

Figure 7. Percent area fished vs. landings value (euro) by métier, coloured by year. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 8

Figure 8. The area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018. The lightest blue c-squares represent the lowest 10% of total SAR / value of landings. The brown c-squares represent the highest 10% of total SAR / value of landings.

Fishing by métier

Intensity and weight of landings are estimated for the grid cells that were fished by one MBCG métier, ignoring cells fished by other métiers (Table 3).

The métier with the highest landings and value per area fished is the otter trawling for small pelagic fish (OT_SPF), but it should be noted that only a very small area has been fished by this métier. The seines (SDN_DMF and SSC_DMF) have the lowest landings and value per area fished. This is followed by otter trawls that target demersal fish (OT_DMF).

Table 3

Table 3. Overview of area fished (sum of swept area), landings and value for the different metiers. Area fished in 1000 km2, weight of landings in 1000 tonnes, value of landings in 10^6 euro.

	DRB_MOL	OT_CRU	OT_DMF	OT_MI	OT_SPF	SDN_DMF	SSC_DMF	TBB_CRU	TBB_DMF	TBB_MOL
Area swept (1000 km2)	8.15	154.88	761.85	25.05	0.27	17.06	59.40	0.01	22.23	<0.005
Landings (1000 tonnes)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)	32.39	77.69	263.54	21.90	5.09	1.82	10.66	0.02	36.89	<0.005
Landings (1000 tonnes)/Area swept (1000 km2)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)/Area swept (1000 km2)	3.97	0.50	0.35	0.87	19.14	0.11	0.18	2.40	1.66	10.59

Impact

No information available

Management scenarios

The figures and tables below show one implementation of multi-purpose habitat management through reductions in effort and spatial closures for the four most extensive MSFD habitat types. They show the unfished area of landings based on a static assessment of effort removal. No impact data is available for this subdivision at present.

The analysis is based on the progressive removal of 5 to 99% of all MBCG fishing effort, starting from the c-squares with the lowest effort (corrected for the areal extent of the MSFD habitat within each c-square). Blue dots show the current situation and are used as reference. The % of unfished area in the reference is only based on grid cells that are unfished.

For all habitats the %unfished drops much faster than the value of the fishery.

MSFD habitat - 1

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	12.66	100.00	NA
5	NA	NA	52.82	90.54	NA
10	NA	NA	61.23	83.63	NA
15	NA	NA	66.71	77.58	NA
20	NA	NA	70.88	72.04	NA
30	NA	NA	77.68	60.70	NA
40	NA	NA	83.00	50.44	NA
60	NA	NA	91.06	32.11	NA
80	NA	NA	96.63	15.37	NA
99	NA	NA	99.90	0.96	NA

MSFD habitat - 2

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	6.51	100.00	NA
5	NA	NA	33.12	91.54	NA
10	NA	NA	42.72	84.60	NA
15	NA	NA	50.34	78.62	NA
20	NA	NA	56.70	73.12	NA
30	NA	NA	67.03	63.22	NA
40	NA	NA	75.41	53.40	NA
60	NA	NA	87.79	34.19	NA
80	NA	NA	95.90	16.09	NA
99	NA	NA	99.93	0.52	NA

MSFD habitat - 3

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	1.41	100.00	NA
5	NA	NA	27.77	94.59	NA
10	NA	NA	39.77	89.86	NA
15	NA	NA	49.12	85.48	NA
20	NA	NA	56.39	81.30	NA
30	NA	NA	67.60	72.90	NA
40	NA	NA	75.86	63.98	NA
60	NA	NA	87.62	44.90	NA
80	NA	NA	95.77	24.03	NA
99	NA	NA	99.91	1.23	NA

MSFD habitat - 4

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	41.25	100.00	NA
5	NA	NA	67.63	93.01	NA
10	NA	NA	73.60	87.32	NA
15	NA	NA	77.67	81.52	NA
20	NA	NA	80.86	75.91	NA
30	NA	NA	85.64	64.87	NA
40	NA	NA	89.08	55.42	NA
60	NA	NA	94.23	35.74	NA
80	NA	NA	97.92	15.95	NA
99	NA	NA	99.97	0.30	NA

Overview all MSFD habitats

Fishing effort consequences, as a % relative to total swept area, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral coarse sediment	142.4	0.0	0.0	<0.1	0.3	1.2	3.8	9.1	18.9	34.1	57.0
Offshore circalittoral sand	127.07	0.0	<0.1	0.9	3.7	8.4	14.7	23.0	33.3	46.5	64.7
Offshore circalittoral mud	64.6	<0.1	0.5	2.6	5.8	10.1	15.5	22.9	32.8	46.2	65.1
Upper bathyal sediment	156.59	0.0	0.0	0.0	0.0	0.0	0.1	1.4	6.7	18.6	43.0
Upper bathyal sediment or Upper bathyal rock and biogenic reef	43.13	0.0	0.0	0.0	0.0	<0.1	0.1	0.4	1.0	5.7	29.2
Unknown	42.64	0.0	0.0	0.0	0.0	0.2	0.8	2.0	4.4	13.8	42.3
Offshore circalittoral mixed sediment	9.41	0.0	0.0	0.0	<0.1	0.4	0.9	2.2	6.1	15.7	36.4
Offshore circalittoral rock and biogenic reef	6.82	0.0	0.0	0.0	0.3	1.3	2.9	6.2	11.1	20.0	35.4
Circalittoral coarse sediment	20.6	0.0	0.0	0.0	<0.1	0.7	2.2	5.0	10.0	19.0	34.9
Circalittoral sand	11.16	0.0	0.0	0.0	0.0	<0.1	0.8	2.5	6.6	15.9	36.4
Circalittoral mud	4.82	0.0	0.0	0.0	0.2	0.7	2.7	5.7	12.1	26.5	55.2
Circalittoral rock and biogenic reef	9.27	0.0	0.0	0.0	0.0	0.0	0.4	2.6	7.3	18.3	42.4
Infralittoral sand	1.96	0.0	0.0	0.0	0.0	0.0	<0.1	0.3	1.4	4.9	27.7
Infralittoral coarse sediment	1.27	0.0	0.0	0.0	0.0	<0.1	0.3	1.2	4.2	9.4	22.3
Circalittoral mixed sediment	0.96	0.0	0.0	0.0	<0.1	0.5	2.4	9.2	19.6	32.4	69.6
Infralittoral rock and biogenic reef	1.96	0.0	0.0	0.0	0.0	0.0	<0.1	0.5	2.2	7.0	23.1
Lower bathyal sediment	117.09	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Upper bathyal rock and biogenic reef	0.82	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.3	5.3
Abyssal	139.78	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Lower bathyal sediment or Lower bathyal rock and biogenic reef	33.97	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	2.9
Infralittoral mud	0.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.6	8.1	27.2
Infralittoral mixed sediment	0.19	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.5	2.2	7.2
Lower bathyal rock and biogenic reef	0.48	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Fishing value consequences, as a % relative to total value, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral coarse sediment	142.4	<0.1	<0.1	0.2	1.1	2.8	7.4	15.3	26.5	43.6	65.2
Offshore circalittoral sand	127.07	<0.1	0.3	2.0	6.6	13.2	21.0	29.9	40.1	52.7	70.1
Offshore circalittoral mud	64.6	0.1	0.7	3.2	6.2	10.2	15.0	21.2	29.6	41.7	60.4
Upper bathyal sediment	156.59	0.0	0.0	0.0	0.0	<0.1	0.3	2.5	9.0	22.4	47.5
Upper bathyal sediment or Upper bathyal rock and biogenic reef	43.13	<0.1	<0.1	<0.1	<0.1	<0.1	0.4	1.1	2.5	10.7	38.6
Unknown	42.64	<0.1	<0.1	<0.1	<0.1	0.7	2.2	5.7	10.4	23.8	49.7
Offshore circalittoral mixed sediment	9.41	0.0	0.0	0.0	0.1	1.1	2.0	4.4	11.2	26.3	54.0
Offshore circalittoral rock and biogenic reef	6.82	<0.1	<0.1	<0.1	1.1	3.0	5.7	10.8	16.7	24.4	37.7
Circalittoral coarse sediment	20.6	0.0	0.0	0.0	0.2	1.4	3.1	6.6	11.5	21.8	42.5
Circalittoral sand	11.16	0.0	0.0	0.0	<0.1	0.3	2.4	6.8	15.7	28.5	50.4
Circalittoral mud	4.82	0.0	0.0	0.0	0.5	1.9	5.7	10.9	18.3	34.0	60.3
Circalittoral rock and biogenic reef	9.27	0.0	0.0	<0.1	<0.1	<0.1	1.2	7.4	15.8	30.5	56.4
Infralittoral sand	1.96	0.0	0.0	0.0	0.0	0.0	<0.1	0.8	4.1	13.9	40.0
Infralittoral coarse sediment	1.27	0.0	0.0	0.0	0.0	<0.1	0.3	1.7	5.4	12.9	36.4
Circalittoral mixed sediment	0.96	0.0	0.0	0.0	<0.1	1.4	5.3	15.0	29.5	43.9	78.3
Infralittoral rock and biogenic reef	1.96	0.0	0.0	<0.1	<0.1	<0.1	<0.1	1.4	5.9	15.1	32.5
Lower bathyal sediment	117.09	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Upper bathyal rock and biogenic reef	0.82	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.2	3.4
Abyssal	139.78	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Lower bathyal sediment or Lower bathyal rock and biogenic reef	33.97	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	3.5
Infralittoral mud	0.4	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.7	5.1	26.5
Infralittoral mixed sediment	0.19	0.0	0.0	0.0	0.0	0.0	0.0	0.0	2.3	9.2	22.8
Lower bathyal rock and biogenic reef	0.48	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Fishing weight consequences, as a % relative to total weight, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral coarse sediment	142.4	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral sand	127.07	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mud	64.6	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal sediment	156.59	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal sediment or Upper bathyal rock and biogenic reef	43.13	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Unknown	42.64	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mixed sediment	9.41	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral rock and biogenic reef	6.82	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral coarse sediment	20.6	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral sand	11.16	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mud	4.82	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral rock and biogenic reef	9.27	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral sand	1.96	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral coarse sediment	1.27	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mixed sediment	0.96	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral rock and biogenic reef	1.96	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Lower bathyal sediment	117.09	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal rock and biogenic reef	0.82	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Abyssal	139.78	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Lower bathyal sediment or Lower bathyal rock and biogenic reef	33.97	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mud	0.4	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mixed sediment	0.19	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Lower bathyal rock and biogenic reef	0.48	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

Northern area

Summary

The physical disturbance pressures from mobile bottom-contacting fishing gears varies spatially in the nortern Celtic Seas subdivision, with 83% of the grid cells (I-2), and 53% of the surface area (I-3) being fished on average per year for the period 2013-2018 (Table 1) at depths <200m. Fishing is aggregated with 90% of the pressure occurring in 36% of grid cells (I-4). The area deeper than 200m is more intensely fished.

No longevity layer was available for the Northern area subdivision – declines in community biomass relating to impact cannot, therefore, be calculated for either the L1 or PD method.

Maps of spatial distribution of surface abrasion, economic value and weight of fisheries landings are shown in Figure 1. It is evident from the value map that there is a mistake in the weights for the region, and values are not presented in further analyses.

Table 1

Table 1. Pressure and impact indicators for 2013-2018

Indicators	0 to 200 m	200 to 800 m	more than 800 m
Average intensity (I-1)	1.52	3.49	0
Proportion of area in fished cells (I-2)	0.86	0.82	0
Proportion of area fished per year (I-3)	0.55	0.62	0
Smallest prop. of area in fished cells with 90% of fishing effort (I-4)	0.41	0.38	0
Proportion of area in unfished cells (I-5)	0.14	0.18	1
Average PD impact (I-6)	NA	NA	NA
Average L1 impact (I-6)	NA	NA	NA
Proportion of area with PD impact < 0.2 (I-7)	NA	NA	NA
Proportion of area with L1 impact < 0.2 (I-7)	NA	NA	NA

Figure 1

Figure 1 Geographic distribution of surface abrasion, seabed sensitivity (not shown) and total value and weight from mobile bottom-contacting gear. The maps of surface abrasion, value and weight show the average per year for 2013-2018

Pressure

The distribution of fishing intensity in the Northern area subdivision has a strong spatial variation (Figure 2), with high concentrations of fishing effort occurring along the shelf edge. Areas with lower intensity occur in coastal waters to the northwest of mainland Scotland.

The proportion of the area subject to fishing pressure differs between broad-scale habitats and is highest in offshore circalittoral mud (99% of grid cells fished) and offshore circalittoral sand (93% of grid cells fished) (Table 2). Fishing intensity is highest in offshore circalittoral mud (average intensity = 3.67 year-1) and offshore circalittoral sand (average intensity = 1.91 year-1).

Total fishing intensity remained unchanged over time until an elevation in 2016 - 2018 (Figure 3). This has been driven by an increase in the intensity in upper bathyal sediment, and, to an extent, offshore circalittoral sand, since 2016. Average trawling intensity is more variable over time than the proportion of area fished (Figure 3, compare left and middle panel), with the exception of a strong, single-year reduction in most seafloor categories in 2017. Taken over the 10 year reporting period, this comparison shows that changes in intensity have not affected greatly the spatial distribution of the footprint.

Fishing pressure is aggregated at the level of the habitat (Figure 3, right panel). In all but abyssal areas, which are subject to a very small fishing footprint, the smallest proportion of habitat with 90% of effort varies between 20-48%, with the exception of 2017 where a footprint < 10% was recorded in offshore circalittoral coarse sediment. The intensively fished areas represent the ‘core fishing grounds’. These grounds contribute most of the landings (Figure 4). More than 80% of the fishing effort (swept area) and 75% of the landings, occur in only 20% of the surface area of the Northern area subdivision (Figure 4).

Figure 2

Figure 2 Surface abrasion, Swept Area Ratio, by mobile bottom-contacting gears (year-1), averaged for the 2013-2018 six-year cycle

Table 2

Table 2 Overview of pressure indicators of all mobile bottom-contacting gears per broad-scale habitat averaged for 2013-2018. I refers to the indicators in Table 1.

MSFD broad habitat type	Extent of habitat (1000 km2)	Number of grid cells	Landings 1000 tonnes	Value 106 euro	Swept area 1000 km2	Average intensity (I-1)	Prop. of area in fished grid cells (I-2)	Prop. of area fished per year (I-3)	Smallest prop. of area with 90% of fishing effort (I-4)
Upper bathyal sediment	32.98	2415	NA	15.00	69.22	2.10	0.51	0.39	0.24
Offshore circalittoral sand	21.06	2069	NA	20.05	48.76	2.32	0.95	0.76	0.42
Offshore circalittoral coarse sediment	22.45	2170	NA	16.21	24.51	1.09	0.86	0.46	0.32
Offshore circalittoral mud	0.81	128	NA	1.64	3.32	4.08	0.99	0.95	0.40
Offshore circalittoral mixed sediment	0.27	97	NA	0.17	0.46	1.70	0.81	0.55	0.21
Circalittoral rock and biogenic reef	1.29	444	NA	0.33	0.31	0.24	0.69	0.19	0.18
Circalittoral coarse sediment	1.36	447	NA	0.27	0.25	0.18	0.83	0.14	0.23
Unknown	1.02	426	NA	0.28	0.24	0.23	0.62	0.14	0.13
Offshore circalittoral rock and biogenic reef	0.34	381	NA	0.22	0.20	0.58	0.85	0.35	0.22
Infralittoral rock and biogenic reef	0.59	356	NA	0.04	0.04	0.07	0.34	0.05	0.15
Circalittoral sand	0.15	122	NA	0.03	0.04	0.25	0.86	0.21	0.17
Lower bathyal sediment	21.35	1596	NA	0.00	0.01	0.00	0.00	0.00	0.00
Circalittoral mixed sediment	0.06	34	NA	0.01	0.01	0.12	0.39	0.09	0.15
Infralittoral coarse sediment	0.08	92	NA	0.00	0.01	0.08	0.47	0.06	0.11
Infralittoral mixed sediment	0.05	37	NA	0.00	0.01	0.11	0.40	0.10	0.05
Upper bathyal sediment or Upper bathyal rock and biogenic reef	0.17	27	NA	0.00	0.00	0.02	0.00	0.00	0.07
Infralittoral sand	0.02	26	NA	0.00	0.00	0.08	0.54	0.08	0.15
Circalittoral mud	0.04	18	NA	0.00	0.00	0.00	0.11	0.00	0.11
Infralittoral mud	0.02	21	NA	0.00	0.00	0.00	0.13	0.00	0.14
Abyssal	0.02	4	NA	0.00	0.00	0.00	0.00	0.00	NA
Lower bathyal sediment or Lower bathyal rock and biogenic reef	0.49	78	NA	0.00	0.00	0.00	0.00	0.00	NA

Figure 3

Figure 3. Time series of (a) mean fishing intensity (surface abrasion), (b) proportion of the surface area of the seafloor fished, (c) aggregation of fishing (proportion of the surface area with 90% of the fishing effort) by habitat. Results represent vessels over 15m (2009-2011) and vessels over 12m (2012-2018).

Figure 4

Figure 4. Cumulative proportion of the swept area, landings and value. Grid cells were sorted from highest to lowest fishing intensity and include non-fished cells. The results are for all mobile bottom-contacting gears based on averaged fishing data per c-square from 2013-2018.

Core fishing grounds

Core fishing grounds are defined as the c-squares with the 90% highest value of landings in the VMS data. Figure 5 shows the number of years c-squares are within the 90% highest value by métier. If fishing in a métier occurs in the same c-square every year with high value of landings, the rightmost bar in Figure 5 and 6 will be high, meaning that the c-square is within the 90% highest value of landings every year during the period 2013-2018. If a c-square is only within the 90% highest value in one year, it will end up in the bar at the left. Figure 6 shows the percentage area overlap between the 90% highest value per year and the reference fishing ground. Both figures highlight that otter trawling for small pelagic and mixed fish (OT_SPF, OT_MIX) and the seine (SSC_DMF, SDN_DMF) have the highest variation in space.

Figure 7 illustrates the relationship between area fished in percent and the cumulated value of landings, sorted from the c-squares with highest value fisheries. The curves are start steeply, illustrating the concentration of the fisheries at fishing grounds, and their horizontal component illustrate that peripheral fisheries exist outside the main fishing grounds.

Figure 8 shows the area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018.

Figure 5

Figure 5. Number of years c-squares are within the 90% highest value by métier, presented as a % relative to the total number of c-squares (n) that are within the 90% highest value by métier across all years. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 6

Figure 6. Percentage area overlap between the 90% highest value per year and the reference core fishing ground. For métiers that are included in Figure 5 and missing in Figure 6, no reference core ground could be established and/or métiers were not used in the area in some years.

Figure 7

Figure 7. Percent area fished vs. landings value (euro) by métier, coloured by year. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 8

Figure 8. The area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018. The lightest blue c-squares represent the lowest 10% of total SAR / value of landings. The brown c-squares represent the highest 10% of total SAR / value of landings.

Fishing by métier

Intensity, weight of landings are estimated for the grid cells that were fished by one MBCG métier, ignoring cells fished by other métiers (Table 3).

The métier with the highest landings per area fished is the otter trawling for demersal fish species (OT_DMF). The seines (SDN_DMF and SSC_DMF) and otter trawling for crustaceans (OT_CRU) have the lowest landings per area fished. This is followed by otter trawls that target demersal fish (OT_DMF).

Table 3

Table 3. Overview of area fished (sum of swept area), landings and value for the different metiers. Area fished in 1000 km2, weight of landings in 1000 tonnes, value of landings in 10^6 euro.

	DRB_MOL	OT_CRU	OT_DMF	OT_MI	OT_SPF	SDN_DMF	SSC_DMF	TBB_CRU	TBB_DMF	TBB_MOL
Area swept (1000 km2)	0.21	0.13	126.53	1.64	0.01	11.07	7.90	0	0	0
Landings (1000 tonnes)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)	0.68	0.02	46.59	1.13	2.32	1.00	2.61	0	0	0
Landings (1000 tonnes)/Area swept (1000 km2)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)/Area swept (1000 km2)	3.17	0.17	0.37	0.69	165.69	0.09	0.33	NA	NA	NA

Impact

No information available

Management scenarios

The figures and tables below show one implementation of multi-purpose habitat management through reductions in effort and spatial closures for the four most extensive MSFD habitat types. They show the unfished area of landings based on a static assessment of effort removal. No impact data is available for this subdivision at present.

The analysis is based on the progressive removal of 5 to 99% of all MBCG fishing effort, starting from the c-squares with the lowest effort (corrected for the areal extent of the MSFD habitat within each c-square). Blue dots show the current situation and are used as reference. The % of unfished area in the reference is only based on grid cells that are unfished.

For all habitats the % unfished drops much faster than the value of the fishery.

MSFD habitat - 1

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	48.86	100.00	NA
5	NA	NA	70.07	93.88	NA
10	NA	NA	75.62	89.20	NA
15	NA	NA	79.42	84.92	NA
20	NA	NA	82.37	80.56	NA
30	NA	NA	86.86	72.47	NA
40	NA	NA	90.36	64.48	NA
60	NA	NA	95.22	43.87	NA
80	NA	NA	98.36	21.87	NA
99	NA	NA	100.00	0.54	NA

MSFD habitat - 2

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	4.81	100.00	NA
5	NA	NA	32.36	90.49	NA
10	NA	NA	43.18	84.30	NA
15	NA	NA	51.58	78.91	NA
20	NA	NA	58.62	72.98	NA
30	NA	NA	69.87	63.36	NA
40	NA	NA	78.54	54.54	NA
60	NA	NA	89.71	38.23	NA
80	NA	NA	96.26	19.13	NA
99	NA	NA	99.93	1.28	NA

MSFD habitat - 3

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	14.03	100.00	NA
5	NA	NA	52.05	91.81	NA
10	NA	NA	61.38	85.07	NA
15	NA	NA	67.82	79.84	NA
20	NA	NA	73.37	73.65	NA
30	NA	NA	81.36	62.79	NA
40	NA	NA	86.79	53.03	NA
60	NA	NA	94.29	28.66	NA
80	NA	NA	98.22	11.55	NA
99	NA	NA	100.00	0.33	NA

MSFD habitat - 4

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	0.76	100.00	NA
5	NA	NA	16.60	96.11	NA
10	NA	NA	27.38	92.70	NA
15	NA	NA	36.76	89.63	NA
20	NA	NA	45.68	86.54	NA
30	NA	NA	62.85	79.12	NA
40	NA	NA	71.43	70.25	NA
60	NA	NA	85.42	50.60	NA
80	NA	NA	94.48	26.43	NA
99	NA	NA	100.00	6.59	NA

Overview all MSFD habitats

Fishing effort consequences, as a % relative to total swept area, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Upper bathyal sediment	32.98	0.0	0.0	0.0	0.0	0.0	<0.1	0.7	5.0	15.9	38.7
Offshore circalittoral sand	21.06	<0.1	0.1	1.4	4.0	8.4	14.0	21.1	30.3	42.2	60.8
Offshore circalittoral coarse sediment	22.45	0.0	0.0	<0.1	0.5	1.6	4.3	9.1	16.9	28.3	47.9
Offshore circalittoral mud	0.81	0.5	2.2	6.8	12.2	17.5	23.0	28.8	40.1	51.2	73.8
Offshore circalittoral mixed sediment	0.27	0.0	0.0	<0.1	0.3	2.5	4.8	14.8	27.7	43.1	61.5
Circalittoral rock and biogenic reef	1.29	0.0	0.0	0.0	0.0	0.2	1.6	4.4	12.7	28.5	52.9
Circalittoral coarse sediment	1.36	0.0	0.0	0.2	1.8	4.4	9.9	13.6	22.9	35.9	51.8
Unknown	1.02	0.0	0.0	0.0	0.0	<0.1	0.8	3.4	7.2	15.2	24.6
Offshore circalittoral rock and biogenic reef	0.34	0.0	0.0	0.1	1.3	2.8	6.8	11.2	21.4	34.8	50.1
Infralittoral rock and biogenic reef	0.59	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.2	3.5	19.5
Circalittoral sand	0.15	0.0	0.0	0.3	1.1	5.5	10.9	18.2	23.6	40.4	58.1
Lower bathyal sediment	21.35	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Circalittoral mixed sediment	0.06	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.9	9.8	13.1
Infralittoral coarse sediment	0.08	0.0	0.0	0.0	0.0	0.0	0.0	0.5	2.2	10.8	22.0
Infralittoral mixed sediment	0.05	0.0	0.0	0.0	0.0	0.0	0.0	0.0	1.0	2.2	7.8
Upper bathyal sediment or Upper bathyal rock and biogenic reef	0.17	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Infralittoral sand	0.02	0.0	0.0	0.0	0.0	0.0	7.6	7.6	15.0	35.1	100.0
Circalittoral mud	0.04	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	9.9
Infralittoral mud	0.02	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	<0.1
Abyssal	0.02	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN
Lower bathyal sediment or Lower bathyal rock and biogenic reef	0.49	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN

Fishing value consequences, as a % relative to total value, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Upper bathyal sediment	32.98	0.0	0.0	<0.1	<0.1	<0.1	<0.1	1.1	6.1	16.0	34.2
Offshore circalittoral sand	21.06	<0.1	0.4	2.7	8.0	14.1	20.1	28.2	37.0	47.1	62.4
Offshore circalittoral coarse sediment	22.45	0.0	<0.1	0.3	2.1	3.6	7.2	13.9	22.5	35.5	57.1
Offshore circalittoral mud	0.81	0.5	2.0	5.4	8.4	12.3	15.3	20.2	30.4	41.8	68.2
Offshore circalittoral mixed sediment	0.27	0.0	0.0	0.2	3.0	7.4	11.0	28.6	45.4	59.6	74.0
Circalittoral rock and biogenic reef	1.29	0.0	0.0	0.0	0.0	0.5	8.5	11.4	20.5	31.9	61.6
Circalittoral coarse sediment	1.36	0.0	0.0	0.4	2.2	5.9	13.4	18.0	27.2	39.3	61.8
Unknown	1.02	0.0	0.0	0.0	0.0	0.5	1.6	3.8	7.4	11.3	20.1
Offshore circalittoral rock and biogenic reef	0.34	0.0	0.0	0.4	7.4	9.4	13.7	17.4	26.3	37.4	46.7
Infralittoral rock and biogenic reef	0.59	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.6	12.0	30.6
Circalittoral sand	0.15	0.0	0.0	1.2	3.4	9.7	21.8	32.4	41.3	59.5	67.7
Lower bathyal sediment	21.35	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN
Circalittoral mixed sediment	0.06	0.0	0.0	0.0	0.0	0.0	0.0	0.0	3.1	33.8	35.3
Infralittoral coarse sediment	0.08	0.0	0.0	0.0	0.0	0.0	0.0	1.9	6.4	22.7	58.5
Infralittoral mixed sediment	0.05	0.0	0.0	0.0	0.0	0.0	0.0	0.0	8.2	13.2	33.3
Upper bathyal sediment or Upper bathyal rock and biogenic reef	0.17	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Infralittoral sand	0.02	0.0	0.0	0.0	0.0	0.0	2.0	2.0	6.0	24.1	100.0
Circalittoral mud	0.04	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	<0.1
Infralittoral mud	0.02	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	21.2
Abyssal	0.02	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN
Lower bathyal sediment or Lower bathyal rock and biogenic reef	0.49	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN	NaN

Fishing weight consequences, as a % relative to total weight, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Upper bathyal sediment	32.98	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral sand	21.06	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral coarse sediment	22.45	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mud	0.81	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mixed sediment	0.27	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral rock and biogenic reef	1.29	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral coarse sediment	1.36	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Unknown	1.02	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral rock and biogenic reef	0.34	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral rock and biogenic reef	0.59	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral sand	0.15	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Lower bathyal sediment	21.35	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mixed sediment	0.06	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral coarse sediment	0.08	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mixed sediment	0.05	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal sediment or Upper bathyal rock and biogenic reef	0.17	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral sand	0.02	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mud	0.04	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mud	0.02	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Abyssal	0.02	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Lower bathyal sediment or Lower bathyal rock and biogenic reef	0.49	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

Offshore deep

Summary

The physical disturbance pressures from mobile bottom-contacting fishing gears varies spatially in the offshore deep subdivision, with 81% of the grid cells (I-2), and 43% of the surface area (I-3) being fished on average per year for the period 2013-2018 (Table 1) at depths <200, and with 73% of the grid cells (I-2), and 49% of the surface area (I-3) being fished on average per year for the period 2013-2018 at depths from 200 to 800m. Fishing is aggregated with 90% of the pressure occurring in ~33 of grid cells (I-4). The offshore deep encompasses a considerable area below 800 m which is barely fished.

No longevity layer was available for the Celtic Sea region – declines in community biomass relating to impact cannot, therefore, be calculated for either the L1 or PD method.

Maps of spatial distribution of surface abrasion, economic value and weight of fisheries landings are shown in Figure 1. It is evident from the weight map that there is a mistake in the weights for the region, and weights are not presented in further analyses.

Table 1

Table 1. Pressure and impact indicators for 2013-2018

Indicators	0 to 200 m	200 to 800 m	more than 800 m
Average intensity (I-1)	0.99	1.61	0.03
Proportion of area in fished cells (I-2)	0.81	0.73	0.12
Proportion of area fished per year (I-3)	0.43	0.49	0.02
Smallest prop. of area in fished cells with 90% of fishing effort (I-4)	0.34	0.33	0.02
Proportion of area in unfished cells (I-5)	0.19	0.27	0.88
Average PD impact (I-6)	NA	NA	NA
Average L1 impact (I-6)	NA	NA	NA
Proportion of area with PD impact < 0.2 (I-7)	NA	NA	NA
Proportion of area with L1 impact < 0.2 (I-7)	NA	NA	NA

Figure 1

Figure 1 Geographic distribution of surface abrasion, seabed sensitivity (not shown) and total value and weight from mobile bottom-contacting gear. The maps of surface abrasion, value and weight show the average per year for 2013-2018

Pressure

The distribution of fishing intensity in the Offshore deep subdivision has a strong spatial variation (Figure 2), with high concentrations of fishing effort occurring along the shelf edge and the waters around Rockall.

The most fishing habitat is the Upper bathyal sediment at an average intensity of 1.17y-1. The proportion of the area subject to fishing pressure differs between broad-scale habitats and is highest in UNKNOWN (100% of grid cells fished) and offshore circalittoral mud (94% of grid cells fished) (Table 2). Fishing intensity is highest in offshore circalittoral mud (average intensity = 0.85 year-1) and offshore circalittoral sand (average intensity = 2.14 year-1). C-squares containing Offshore circalittoral rock and biogenic reef are fished at a very high intensity of 16.30y-1, although is probably that this is cause by the concentration of this feature in cells with other more fishable habitats.

Total fishing intensity was largely unchanged over time (Figure 3), with the exception of a single year reduction in 2010. This reduction in fishing intensity was evident in both the upper bathyal sediment and the upper bathyal sediment or upper bathyal rock and biogenic reef. Average trawling intensity is more variable over time than the proportion of area fished (Figure 3, compare left and middle panel), with the exception of a strong, single-year reduction in 2010. Taken over the 10 year reporting period, this comparison shows that changes in intensity have not affected greatly the spatial distribution of the footprint.

Fishing pressure is aggregated at the level of the habitat (Figure 3, right panel). In all but abyssal areas and lower bathyal sediment, which are subject to a very small fishing footprint, the smallest proportion of habitat with 90% of effort varies between 15-30%. The intensively fished areas represent the ‘core fishing grounds’. These grounds contribute most of the landings and value (Figure 4). Close to 100% of the fishing effort (swept area) and 100% of the landings and value, occur in only 20% of the surface area of the Offshore Deep Subdivision (Figure 4).

Figure 2

Figure 2 Surface abrasion, Swept Area Ratio, by mobile bottom-contacting gears (year-1), averaged for the 2013-2018 six-year cycle

Table 2

Table 2 Overview of pressure indicators of all mobile bottom-contacting gears per broad-scale habitat averaged for 2013-2018. I refers to the indicators in Table 1.

MSFD broad habitat type	Extent of habitat (1000 km2)	Number of grid cells	Landings 1000 tonnes	Value 106 euro	Swept area 1000 km2	Average intensity (I-1)	Prop. of area in fished grid cells (I-2)	Prop. of area fished per year (I-3)	Smallest prop. of area with 90% of fishing effort (I-4)
Upper bathyal sediment	119.10	7659	NA	62.18	139.81	1.17	0.59	0.37	0.22
Upper bathyal sediment or Upper bathyal rock and biogenic reef	41.63	2587	NA	9.84	28.06	0.67	0.61	0.21	0.13
Offshore circalittoral mud	7.11	598	NA	3.42	6.05	0.85	0.94	0.57	0.41
Offshore circalittoral coarse sediment	2.10	222	NA	2.30	3.39	1.61	0.93	0.56	0.33
Offshore circalittoral rock and biogenic reef	0.16	25	NA	1.54	2.53	16.30	0.90	0.69	0.16
Offshore circalittoral sand	0.26	51	NA	0.34	0.56	2.14	0.83	0.68	0.29
Unknown	0.17	35	NA	0.15	0.35	2.14	1.00	0.78	0.46
Lower bathyal sediment	95.74	6374	NA	0.22	0.29	0.00	0.06	0.00	0.03
Upper bathyal rock and biogenic reef	0.81	319	NA	0.15	0.17	0.21	0.24	0.09	0.05
Abyssal	139.76	8088	NA	0.23	0.17	0.00	0.04	0.00	0.02
Lower bathyal sediment or Lower bathyal rock and biogenic reef	33.48	2198	NA	0.18	0.11	0.00	0.14	0.00	0.07
Offshore circalittoral mixed sediment	0.98	177	NA	0.01	0.02	0.02	0.57	0.02	0.34
Lower bathyal rock and biogenic reef	0.48	179	NA	0.00	0.00	0.00	0.01	0.00	0.01

Figure 3

Figure 3. Time series of (a) mean fishing intensity (surface abrasion), (b) proportion of the surface area of the seafloor fished, (c) aggregation of fishing (proportion of the surface area with 90% of the fishing effort) by habitat. Results represent vessels over 15m (2009-2011) and vessels over 12m (2012-2018).

Figure 4

Figure 4. Cumulative proportion of the swept area, landings and value. Grid cells were sorted from highest to lowest fishing intensity and include non-fished cells. The results are for all mobile bottom-contacting gears based on averaged fishing data per c-square from 2013-2018.

Core fishing grounds

Core fishing grounds are defined as the c-squares with the 90% highest value of landings in the VMS data. Figure 5 shows the number of years c-squares are within the 90% highest value by métier. If fishing in a métier occurs in the same c-square every year with high value of landings, the rightmost bar in Figure 5 will be high, meaning that the c-square is within the 90% highest value of landings every year during the period 2013-2018. If a c-square is only within the 90% highest value in one year, it will end up in the bar at the left. Figure 6 shows the percentage area overlap between the 90% highest value per year and the reference fishing ground. Both figures highlight that otter trawling for mixed fish and small pelagic species (OT_MIX, OT_SPF), fishing with dredges for scallops and mussels (DRB_MOL), and seine fishing for demersal fish (SSC_DMF) have the highest variation in space.

Figure 7 illustrates the relationship between area fished in percent and the cumulated value of landings, sorted from the c-squares with highest value fisheries. The curves are start steeply, illustrating the concentration of the fisheries at fishing grounds, and their horizontal component illustrate that peripheral fisheries exist outside the main fishing grounds.

Figure 8 shows the area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018.

Figure 5

Figure 5. Number of years c-squares are within the 90% highest value by métier, presented as a % relative to the total number of c-squares (n) that are within the 90% highest value by métier across all years. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 6

Figure 6. Percentage area overlap between the 90% highest value per year and the reference core fishing ground. For métiers that are included in Figure 5 and missing in Figure 6, no reference core ground could be established and/or métiers were not used in the area in some years.

Figure 7

Figure 7. Percent area fished vs. landings value (euro) by métier, coloured by year. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 8

Figure 8. The area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018. The lightest blue c-squares represent the lowest 10% of total SAR / value of landings. The brown c-squares represent the highest 10% of total SAR / value of landings.

Fishing by métier

Intensity, weight and value of landings are estimated for the grid cells that were fished by one MBCG métier, ignoring cells fished by other métiers (Table 3).

The métier with the highest landings and value per area fished is the otter trawling for small pelagic species (OT_SPF). The seines (SDN_DMF and SSC_DMF) have the lowest landings and value per area fished. Landings per area swept are high in this subdivision compared to most other areas.

Table 3

Table 3. Overview of area fished (sum of swept area), landings and value for the different metiers. Area fished in 1000 km2, weight of landings in 1000 tonnes, value of landings in 10^6 euro.

	DRB_MOL	OT_CRU	OT_DMF	OT_MI	OT_SPF	SDN_DMF	SSC_DMF	TBB_CRU	TBB_DMF	TBB_MOL
Area swept (1000 km2)	<0.005	26.70	144.41	10.02	0.07	0.09	0.20	0	<0.005	0
Landings (1000 tonnes)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)	0.02	12.99	56.72	10.28	0.42	0.03	0.09	0	0	0
Landings (1000 tonnes)/Area swept (1000 km2)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)/Area swept (1000 km2)	6.25	0.49	0.39	1.03	5.82	0.33	0.48	NA	0	NA

Impact

No information available

Management scenarios

The figures and tables below show one implementation of multi-purpose habitat management through reductions in effort and spatial closures for the four most extensive MSFD habitat types. They show the unfished area of landings based on a static assessment of effort removal. No impact data is available for this subdivision at present.

The analysis is based on the progressive removal of 5 to 99% of all MBCG fishing effort, starting from the c-squares with the lowest effort (corrected for the areal extent of the MSFD habitat within each c-square). Blue dots show the current situation and are used as reference. The % of unfished area in the reference is only based on grid cells that are unfished.

For all habitats the % unfished drops much faster than the value of the fishery.

MSFD habitat - 1

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	40.71	100.00	NA
5	NA	NA	68.32	93.57	NA
10	NA	NA	74.19	87.94	NA
15	NA	NA	78.20	82.65	NA
20	NA	NA	81.34	77.08	NA
30	NA	NA	86.03	65.96	NA
40	NA	NA	89.39	55.96	NA
60	NA	NA	94.13	36.84	NA
80	NA	NA	97.59	18.49	NA
99	NA	NA	99.92	1.14	NA

MSFD habitat - 2

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	39.40	100.00	NA
5	NA	NA	81.24	89.37	NA
10	NA	NA	85.19	81.63	NA
15	NA	NA	87.44	75.64	NA
20	NA	NA	89.04	70.12	NA
30	NA	NA	91.56	58.84	NA
40	NA	NA	93.45	48.55	NA
60	NA	NA	96.28	31.29	NA
80	NA	NA	98.37	16.12	NA
99	NA	NA	99.95	1.08	NA

MSFD habitat - 3

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	5.70	100.00	NA
5	NA	NA	38.50	95.20	NA
10	NA	NA	46.47	90.01	NA
15	NA	NA	52.28	85.09	NA
20	NA	NA	57.62	79.47	NA
30	NA	NA	66.12	69.61	NA
40	NA	NA	72.93	58.93	NA
60	NA	NA	84.17	39.99	NA
80	NA	NA	93.62	20.49	NA
99	NA	NA	100.00	1.41	NA

MSFD habitat - 4

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	7.12	100.00	NA
5	NA	NA	49.26	96.14	NA
10	NA	NA	55.73	90.96	NA
15	NA	NA	61.67	86.30	NA
20	NA	NA	66.75	81.00	NA
30	NA	NA	76.87	71.41	NA
40	NA	NA	84.25	61.38	NA
60	NA	NA	95.51	41.55	NA
80	NA	NA	99.41	23.06	NA
99	NA	NA	100.00	17.13	NA

Overview all MSFD habitats

Fishing effort consequences, as a % relative to total swept area, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Upper bathyal sediment	119.1	0.0	0.0	0.0	0.0	0.0	0.1	1.3	6.2	17.8	42.2
Upper bathyal sediment or Upper bathyal rock and biogenic reef	41.63	0.0	0.0	0.0	0.0	<0.1	0.1	0.3	0.8	3.8	23.7
Offshore circalittoral mud	7.11	0.0	<0.1	0.7	2.2	5.9	12.9	22.6	36.0	52.4	72.3
Offshore circalittoral coarse sediment	2.1	0.0	<0.1	0.2	0.8	2.4	5.3	14.1	24.2	35.2	50.7
Offshore circalittoral rock and biogenic reef	0.16	0.0	0.0	<0.1	0.7	1.6	1.6	2.6	11.6	60.0	100.0
Offshore circalittoral sand	0.26	0.0	0.0	0.3	1.4	7.8	20.5	33.3	48.9	57.5	87.3
Unknown	0.17	3.0	4.6	5.5	12.2	22.6	29.3	33.3	50.8	50.8	84.2
Lower bathyal sediment	95.74	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Upper bathyal rock and biogenic reef	0.81	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.2	4.7
Abyssal	139.76	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Lower bathyal sediment or Lower bathyal rock and biogenic reef	33.48	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	3.1
Offshore circalittoral mixed sediment	0.98	0.0	0.0	0.0	0.0	0.0	1.9	8.3	17.1	26.4	52.8
Lower bathyal rock and biogenic reef	0.48	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Fishing value consequences, as a % relative to total value, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Upper bathyal sediment	119.1	0.0	0.0	0.0	0.0	0.0	0.3	2.0	7.8	20.5	46.2
Upper bathyal sediment or Upper bathyal rock and biogenic reef	41.63	<0.1	<0.1	<0.1	<0.1	<0.1	0.4	1.1	2.2	8.8	34.3
Offshore circalittoral mud	7.11	0.0	0.1	0.7	2.3	5.8	13.1	23.1	36.5	52.8	72.4
Offshore circalittoral coarse sediment	2.1	0.0	<0.1	0.2	0.7	1.8	4.2	13.4	23.1	34.2	50.0
Offshore circalittoral rock and biogenic reef	0.16	0.0	0.0	<0.1	0.7	1.6	1.6	3.0	14.6	62.3	100.0
Offshore circalittoral sand	0.26	0.0	0.0	0.3	1.7	8.4	19.6	39.7	60.2	67.8	89.7
Unknown	0.17	4.1	6.1	6.7	16.1	30.3	41.6	46.0	60.7	60.7	85.3
Lower bathyal sediment	95.74	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Upper bathyal rock and biogenic reef	0.81	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.2	3.0
Abyssal	139.76	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Lower bathyal sediment or Lower bathyal rock and biogenic reef	33.48	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	3.5
Offshore circalittoral mixed sediment	0.98	0.0	0.0	0.0	0.0	0.0	2.2	9.2	19.5	28.6	65.0
Lower bathyal rock and biogenic reef	0.48	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Fishing weight consequences, as a % relative to total weight, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Upper bathyal sediment	119.1	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal sediment or Upper bathyal rock and biogenic reef	41.63	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mud	7.11	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral coarse sediment	2.1	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral rock and biogenic reef	0.16	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral sand	0.26	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Unknown	0.17	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Lower bathyal sediment	95.74	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal rock and biogenic reef	0.81	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Abyssal	139.76	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Lower bathyal sediment or Lower bathyal rock and biogenic reef	33.48	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mixed sediment	0.98	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Lower bathyal rock and biogenic reef	0.48	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

Irish Sea

Summary

The physical disturbance pressures from mobile bottom-contacting fishing gears varies spatially in the Irish Sea, with 78% of the grid cells (I-2), and 28% of the surface area (I-3) being fished on average per year for the period 2013-2018 (Table 1) at depths <200m. Fishing is aggregated with 90% of the pressure occurring in 17% of grid cells (I-4).

No longevity layer was available for the Irish Sea subdivision – declines in community biomass relating to impact cannot, therefore, be calculated for either the L1 or PD method.

Maps of spatial distribution of surface abrasion, economic value and weight of fisheries landings are shown in Figure 1. It is evident from the weight map that there is a mistake in the weights for the region, and weights are not presented in further analyses.

Table 1

Table 1. Pressure and impact indicators for 2013-2018

Indicators	0 to 200 m	200 to 800 m	more than 800 m
Average intensity (I-1)	1.11	NA	NA
Proportion of area in fished cells (I-2)	0.78	NA	NA
Proportion of area fished per year (I-3)	0.28	NA	NA
Smallest prop. of area in fished cells with 90% of fishing effort (I-4)	0.17	NA	NA
Proportion of area in unfished cells (I-5)	0.22	NA	NA
Average PD impact (I-6)	NA	NA	NA
Average L1 impact (I-6)	NA	NA	NA
Proportion of area with PD impact < 0.2 (I-7)	NA	NA	NA
Proportion of area with L1 impact < 0.2 (I-7)	NA	NA	NA

Figure 1

Figure 1 Geographic distribution of surface abrasion, seabed sensitivity (not shown) and total value and weight from mobile bottom-contacting gear. The maps of surface abrasion, value and weight show the average per year for 2013-2018

Pressure

The distribution of fishing intensity in the Northern area subdivision has a strong spatial variation (Figure 2), with high concentrations of fishing effort occurring centrally and to the north in the Firth of Clyde.

The proportion of the area subject to fishing pressure differs between broad-scale habitats and is highest in offshore circalittoral mud (100% of grid cells fished) and offshore circalittoral sand (97% of grid cells fished) (Table 2). Fishing intensity is highest in offshore circalittoral mud (average intensity = 6.33 year-1) and offshore circalittoral sand (average intensity = 0.75 year-1).

Total fishing intensity remained unchanged over time with the exception of a strong, single-year decline in 2017 (Figure 3). This decline was evident across all habitats but was particularly marked in offshore circalittoral mud, and likely to represent a data error. Average trawling intensity was largely comparable to the proportion of area fished (Figure 3, compare left and middle panel). Taken over the 10 year reporting period, the proportion of area fished was seen to be stable with the exception of 2017.

Fishing pressure is aggregated at the level of the habitat (Figure 3, right panel). The smallest proportion of habitat with 90% of effort varies between 20-50%, with the exception of 2017 where a footprint < 10% was recorded in circalittoral coarse sediment. The intensively fished areas represent the ‘core fishing grounds’. These grounds contribute most of the landings and value (Figure 4). Roughly 90% of the fishing effort (swept area) and almost 80% of the landings and value, occur in only 20% of the surface area of the Irish Sea subdivision (Figure 4).

Figure 2

Figure 2 Surface abrasion, Swept Area Ratio, by mobile bottom-contacting gears (year-1), averaged for the 2013-2018 six-year cycle

Table 2

Table 2 Overview of pressure indicators of all mobile bottom-contacting gears per broad-scale habitat averaged for 2013-2018. I refers to the indicators in Table 1.

MSFD broad habitat type	Extent of habitat (1000 km2)	Number of grid cells	Landings 1000 tonnes	Value 106 euro	Swept area 1000 km2	Average intensity (I-1)	Prop. of area in fished grid cells (I-2)	Prop. of area fished per year (I-3)	Smallest prop. of area with 90% of fishing effort (I-4)
Offshore circalittoral mud	8.08	721	NA	22.95	51.12	6.33	1.00	0.91	0.43
Offshore circalittoral sand	6.95	1025	NA	4.60	5.23	0.75	0.97	0.38	0.24
Offshore circalittoral coarse sediment	15.80	1425	NA	9.32	3.99	0.25	0.91	0.20	0.30
Circalittoral mud	3.00	496	NA	0.64	1.58	0.53	0.78	0.24	0.17
Offshore circalittoral mixed sediment	2.61	568	NA	2.21	1.06	0.41	0.92	0.27	0.22
Circalittoral sand	4.70	883	NA	0.88	0.84	0.18	0.62	0.12	0.14
Circalittoral coarse sediment	5.28	777	NA	1.99	0.83	0.16	0.78	0.13	0.16
Offshore circalittoral rock and biogenic reef	0.88	526	NA	0.24	0.39	0.44	0.97	0.16	0.22
Unknown	2.23	925	NA	0.36	0.38	0.17	0.51	0.09	0.12
Circalittoral rock and biogenic reef	0.85	495	NA	0.33	0.38	0.44	0.83	0.28	0.13
Circalittoral mixed sediment	0.50	253	NA	0.13	0.13	0.26	0.75	0.19	0.19
Infralittoral rock and biogenic reef	0.18	400	NA	0.04	0.06	0.33	0.58	0.13	0.12
Infralittoral coarse sediment	0.48	249	NA	0.24	0.06	0.12	0.53	0.08	0.06
Infralittoral sand	0.92	401	NA	0.14	0.04	0.05	0.41	0.03	0.09
Infralittoral mud	0.20	153	NA	0.08	0.02	0.09	0.48	0.07	0.12
Infralittoral mixed sediment	0.05	80	NA	0.00	0.01	0.15	0.48	0.11	0.11

Figure 3

Figure 3. Time series of (a) mean fishing intensity (surface abrasion), (b) proportion of the surface area of the seafloor fished, (c) aggregation of fishing (proportion of the surface area with 90% of the fishing effort) by habitat. Results represent vessels over 15m (2009-2011) and vessels over 12m (2012-2018).

Figure 4

Figure 4. Cumulative proportion of the swept area, landings and value. Grid cells were sorted from highest to lowest fishing intensity and include non-fished cells. The results are for all mobile bottom-contacting gears based on averaged fishing data per c-square from 2013-2018.

Core fishing grounds

Core fishing grounds are defined as the c-squares with the 90% highest value of landings in the VMS data. Figure 5 shows the number of years c-squares are within the 90% highest value by métier. If fishing in a métier occurs in the same c-square every year with high value of landings, the rightmost bar in Figure 5 will be high, meaning that the c-square is within the 90% highest value of landings every year during the period 2013-2018. If a c-square is only within the 90% highest value in one year, it will end up in the bar at the left. Figure 6 shows the percentage area overlap between the 90% highest value per year and the reference fishing ground. Both figures highlight that otter trawling for demersal fish (OT_DMF, and seine fishing for demersal fish (SSC_DMF) have the highest variation in space.

Figure 7 illustrates the relationship between area fished in percent and the cumulated value of landings, sorted from the c-squares with highest value fisheries. The curves are start steeply, illustrating the concentration of the fisheries at fishing grounds, and their horizontal component illustrate that peripheral fisheries exist outside the main fishing grounds.

Figure 8 shows the area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018.

Figure 5

Figure 5. Number of years c-squares are within the 90% highest value by métier, presented as a % relative to the total number of c-squares (n) that are within the 90% highest value by métier across all years. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 6

Figure 6. Percentage area overlap between the 90% highest value per year and the reference core fishing ground. For métiers that are included in Figure 5 and missing in Figure 6, no reference core ground could be established and/or métiers were not used in the area in some years.

Figure 7

Figure 7. Percent area fished vs. landings value (euro) by métier, coloured by year. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 8

Figure 8. The area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018. The lightest blue c-squares represent the lowest 10% of total SAR / value of landings. The brown c-squares represent the highest 10% of total SAR / value of landings.

Fishing by métier

Intensity, weight and value of landings are estimated for the grid cells that were fished by one MBCG métier, ignoring cells fished by other métiers (Table 3).

The métier with the highest landings and value per area fished is fishing with dredges for scallops and mussels (DRB_MOL) and beam trawl for crustaceans (TBB_CRU). The seine fishery for demersal fish (SDN_DMF and SSC_DMF) and otter trawling for demersal fish (OT_DMF) have the lowest landings and value per area fished.

Table 3

Table 3. Overview of area fished (sum of swept area), landings and value for the different metiers. Area fished in 1000 km2, weight of landings in 1000 tonnes, value of landings in 10^6 euro.

	DRB_MOL	OT_CRU	OT_DMF	OT_MI	OT_SPF	SDN_DMF	SSC_DMF	TBB_CRU	TBB_DMF	TBB_MOL
Area swept (1000 km2)	3.92	52.58	6.12	1.00	0	0	1.32	0.01	1.64	0
Landings (1000 tonnes)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)	15.70	23.54	2.15	0.79	0	0	0.46	0.02	2.01	0
Landings (1000 tonnes)/Area swept (1000 km2)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)/Area swept (1000 km2)	4.01	0.45	0.35	0.80	NA	NA	0.35	2.92	1.23	NA

Impact

No information available

Management scenarios

The figures and tables below show one implementation of multi-purpose habitat management through reductions in effort and spatial closures for the four most extensive MSFD habitat types. They show the unfished area of landings based on a static assessment of effort removal. No impact data is available for this subdivision at present.

The analysis is based on the progressive removal of 5 to 99% of all MBCG fishing effort, starting from the c-squares with the lowest effort (corrected for the areal extent of the MSFD habitat within each c-square). Blue dots show the current situation and are used as reference. The % of unfished area in the reference is only based on grid cells that are unfished.

For all habitats the % unfished drops much faster than the value of the fishery.

MSFD habitat - 1

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	0.13	100.00	NA
5	NA	NA	25.04	94.15	NA
10	NA	NA	32.54	89.60	NA
15	NA	NA	38.70	85.15	NA
20	NA	NA	43.90	80.76	NA
30	NA	NA	53.40	72.22	NA
40	NA	NA	62.15	63.86	NA
60	NA	NA	77.58	45.65	NA
80	NA	NA	90.24	25.19	NA
99	NA	NA	99.77	1.70	NA

MSFD habitat - 2

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	2.87	100.00	NA
5	NA	NA	43.29	92.45	NA
10	NA	NA	58.85	86.62	NA
15	NA	NA	66.95	79.86	NA
20	NA	NA	72.39	72.83	NA
30	NA	NA	81.28	58.91	NA
40	NA	NA	85.64	51.70	NA
60	NA	NA	93.01	31.28	NA
80	NA	NA	97.53	11.54	NA
99	NA	NA	100.00	1.38	NA

MSFD habitat - 3

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	8.92	100.00	NA
5	NA	NA	51.83	97.05	NA
10	NA	NA	63.92	93.39	NA
15	NA	NA	71.06	89.25	NA
20	NA	NA	76.23	85.92	NA
30	NA	NA	83.35	74.00	NA
40	NA	NA	87.96	60.32	NA
60	NA	NA	94.56	33.26	NA
80	NA	NA	98.25	13.45	NA
99	NA	NA	100.00	0.34	NA

MSFD habitat - 4

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	21.94	100.00	NA
5	NA	NA	66.39	87.86	NA
10	NA	NA	73.29	82.94	NA
15	NA	NA	79.35	78.60	NA
20	NA	NA	82.20	72.07	NA
30	NA	NA	86.50	62.76	NA
40	NA	NA	88.69	52.70	NA
60	NA	NA	92.63	35.65	NA
80	NA	NA	97.19	14.90	NA
99	NA	NA	100.00	2.91	NA

Overview all MSFD habitats

Fishing effort consequences, as a % relative to total swept area, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral mud	8.08	0.1	0.4	2.9	8.2	16.4	26.4	37.8	50.0	63.8	79.9
Offshore circalittoral sand	6.95	<0.1	0.2	0.8	2.0	4.0	6.8	10.6	17.7	28.2	49.8
Offshore circalittoral coarse sediment	15.8	0.0	<0.1	0.3	1.0	2.3	4.6	8.1	14.2	25.0	45.1
Circalittoral mud	3	0.0	0.0	0.0	0.1	0.5	1.4	3.4	8.1	18.1	49.6
Offshore circalittoral mixed sediment	2.61	0.0	<0.1	0.3	1.0	2.2	4.3	9.5	17.9	31.4	53.5
Circalittoral sand	4.7	0.0	0.0	0.0	0.0	<0.1	0.3	1.3	3.8	10.3	25.7
Circalittoral coarse sediment	5.28	0.0	0.0	0.0	<0.1	0.5	1.9	4.6	10.5	22.1	43.7
Offshore circalittoral rock and biogenic reef	0.88	<0.1	0.2	0.7	1.8	3.1	4.9	8.1	11.7	17.1	29.6
Unknown	2.23	0.0	0.0	0.0	0.0	0.0	<0.1	0.4	1.7	6.2	17.0
Circalittoral rock and biogenic reef	0.85	0.0	0.0	<0.1	0.3	1.1	3.4	10.0	26.1	44.7	68.2
Circalittoral mixed sediment	0.5	0.0	0.0	0.0	0.1	0.5	2.3	8.9	16.3	31.0	57.6
Infralittoral rock and biogenic reef	0.18	0.0	0.0	0.0	0.0	0.0	<0.1	0.4	1.9	6.7	16.1
Infralittoral coarse sediment	0.48	0.0	0.0	0.0	0.0	0.0	0.1	0.7	1.9	13.8	33.4
Infralittoral sand	0.92	0.0	0.0	0.0	0.0	0.0	0.0	<0.1	2.5	10.4	36.7
Infralittoral mud	0.2	0.0	0.0	0.0	0.0	0.0	0.0	0.8	7.8	13.3	47.9
Infralittoral mixed sediment	0.05	0.0	0.0	0.0	0.0	0.0	0.0	0.5	1.2	2.9	12.2

Fishing value consequences, as a % relative to total value, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral mud	8.08	0.3	0.8	3.8	8.8	16.2	24.9	34.6	45.5	57.7	74.8
Offshore circalittoral sand	6.95	<0.1	0.3	1.2	3.4	6.5	10.0	13.8	23.8	38.5	60.2
Offshore circalittoral coarse sediment	15.8	0.0	<0.1	0.3	0.6	1.3	2.8	5.1	9.7	19.5	46.8
Circalittoral mud	3	0.0	0.0	0.0	0.8	2.0	5.0	10.4	15.8	24.7	55.3
Offshore circalittoral mixed sediment	2.61	0.0	<0.1	0.2	0.7	1.7	3.4	7.9	15.4	30.5	54.6
Circalittoral sand	4.7	0.0	0.0	0.0	0.0	<0.1	1.1	2.7	8.6	20.9	39.5
Circalittoral coarse sediment	5.28	0.0	0.0	0.0	0.1	0.6	2.7	5.5	9.7	22.0	44.0
Offshore circalittoral rock and biogenic reef	0.88	<0.1	1.0	2.6	5.2	8.0	12.8	20.0	28.8	38.0	51.2
Unknown	2.23	0.0	0.0	0.0	0.0	<0.1	<0.1	1.3	5.0	15.4	43.4
Circalittoral rock and biogenic reef	0.85	0.0	0.0	<0.1	0.8	2.4	6.2	13.8	25.7	39.6	68.6
Circalittoral mixed sediment	0.5	0.0	0.0	0.0	0.3	1.5	5.7	17.6	30.4	52.8	71.9
Infralittoral rock and biogenic reef	0.18	0.0	0.0	0.0	0.0	<0.1	0.5	1.7	8.7	23.5	48.1
Infralittoral coarse sediment	0.48	0.0	0.0	0.0	0.0	0.0	0.1	0.6	1.7	10.1	30.8
Infralittoral sand	0.92	0.0	0.0	0.0	0.0	0.0	0.0	<0.1	3.4	11.9	47.3
Infralittoral mud	0.2	0.0	0.0	0.0	0.0	0.0	0.0	0.6	5.3	17.0	56.3
Infralittoral mixed sediment	0.05	0.0	0.0	0.0	0.0	0.0	0.0	1.3	6.3	12.4	31.8

Fishing weight consequences, as a % relative to total weight, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral mud	8.08	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral sand	6.95	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral coarse sediment	15.8	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mud	3	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mixed sediment	2.61	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral sand	4.7	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral coarse sediment	5.28	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral rock and biogenic reef	0.88	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Unknown	2.23	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral rock and biogenic reef	0.85	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mixed sediment	0.5	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral rock and biogenic reef	0.18	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral coarse sediment	0.48	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral sand	0.92	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mud	0.2	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mixed sediment	0.05	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

Centre area

Summary

The physical disturbance pressures from mobile bottom-contacting fishing gears varies spatially in the central Celtic Seas subdivision, with 63% of the grid cells (I-2), and 23% of the surface area (I-3) being fished on average per year for the period 2013-2018 (Table 1). Fishing is aggregated with 90% of the pressure occurring in 17% of grid cells (I-4).

No longevity layer was available for the Centre area subdivision – declines in community biomass relating to impact cannot, therefore, be calculated for either the L1 or PD method.

Maps of spatial distribution of surface abrasion, economic value and weight of fisheries landings are shown in Figure 1. It is evident from the weight map that there is a mistake in the weights for the region, and weights are not presented in further analyses.

Table 1

Table 1. Pressure and impact indicators for 2013-2018

Indicators	0 to 200 m	200 to 800 m	more than 800 m
Average intensity (I-1)	0.51	3.95	NA
Proportion of area in fished cells (I-2)	0.65	1.00	NA
Proportion of area fished per year (I-3)	0.22	0.89	NA
Smallest prop. of area in fished cells with 90% of fishing effort (I-4)	0.17	0.66	NA
Proportion of area in unfished cells (I-5)	0.35	0.00	NA
Average PD impact (I-6)	NA	NA	NA
Average L1 impact (I-6)	NA	NA	NA
Proportion of area with PD impact < 0.2 (I-7)	NA	NA	NA
Proportion of area with L1 impact < 0.2 (I-7)	NA	NA	NA

Figure 1

Figure 1 Geographic distribution of surface abrasion, seabed sensitivity (not shown) and total value and weight from mobile bottom-contacting gear. The maps of surface abrasion, value and weight show the average per year for 2013-2018

Pressure

The distribution of fishing intensity in the Centre area subdivision has a strong spatial variation (Figure 2), with high concentrations of fishing effort occurring along the shelf edge to the west of Ireland. A large area of lower intensity effort occurs to the west of the Outer Hebrides.

The proportion of the area subject to fishing pressure differs between broad-scale habitats and is highest in offshore circalittoral mud (99% of grid cells fished) and offshore circalittoral sand (95% of grid cells fished) (Table 2). Fishing intensity is highest in offshore circalittoral mud (average intensity = 4.08 year-1) and offshore circalittoral sand (average intensity = 2.32 year-1).

Total fishing intensity remained unchanged over time with the exception of a strong, single-year decline in 2017 (Figure 3). This decline was evident across all habitats but was particularly marked in offshore circalittoral mud. Average trawling intensity was largely comparable to the proportion of area fished (Figure 3, compare left and middle panel). Taken over the 10 year reporting period, the proportion of area fished was seen to be stable with the exception of 2017.

Fishing pressure is aggregated at the level of the habitat (Figure 3, right panel). In all areas, the smallest proportion of habitat with 90% of effort varies between 20-40%, with the exception of 2017 where a footprint < 10% was recorded in offshore circalittoral coarse sediment. The intensively fished areas represent the ‘core fishing grounds’. These grounds contribute most of the landings and value (Figure 4). Approximately 90% of the fishing effort (swept area) and 85% of the landings and value, occur in only 20% of the surface area of the Centre area subdivision (Figure 4).

Figure 2

Figure 2 Surface abrasion, Swept Area Ratio, by mobile bottom-contacting gears (year-1), averaged for the 2013-2018 six-year cycle

Table 2

Table 2 Overview of pressure indicators of all mobile bottom-contacting gears per broad-scale habitat averaged for 2013-2018. I refers to the indicators in Table 1.

MSFD broad habitat type	Extent of habitat (1000 km2)	Number of grid cells	Landings 1000 tonnes	Value 106 euro	Swept area 1000 km2	Average intensity (I-1)	Prop. of area in fished grid cells (I-2)	Prop. of area fished per year (I-3)	Smallest prop. of area with 90% of fishing effort (I-4)
Offshore circalittoral mud	12.43	1405	NA	15.68	32.62	2.62	0.96	0.74	0.33
Offshore circalittoral sand	24.31	2897	NA	9.03	16.96	0.70	0.72	0.33	0.18
Upper bathyal sediment	3.39	336	NA	6.62	12.67	3.74	1.00	0.89	0.44
Unknown	31.43	3335	NA	4.13	7.92	0.25	0.63	0.13	0.13
Offshore circalittoral coarse sediment	34.97	3435	NA	6.70	7.07	0.20	0.65	0.13	0.19
Offshore circalittoral mixed sediment	4.09	623	NA	0.98	1.77	0.43	0.62	0.18	0.17
Circalittoral mud	1.26	484	NA	0.89	1.65	1.31	0.83	0.57	0.19
Circalittoral sand	2.78	731	NA	0.56	0.95	0.34	0.58	0.19	0.13
Circalittoral coarse sediment	6.60	1339	NA	1.12	0.80	0.12	0.60	0.10	0.18
Offshore circalittoral rock and biogenic reef	2.93	1416	NA	0.37	0.54	0.18	0.57	0.11	0.15
Circalittoral rock and biogenic reef	4.08	1591	NA	0.40	0.49	0.12	0.40	0.08	0.13
Circalittoral mixed sediment	0.21	208	NA	0.14	0.14	0.67	0.70	0.37	0.22
Infralittoral rock and biogenic reef	0.62	869	NA	0.14	0.14	0.22	0.51	0.13	0.09
Upper bathyal sediment or Upper bathyal rock and biogenic reef	0.03	37	NA	0.06	0.13	3.83	1.00	0.84	0.19
Infralittoral coarse sediment	0.25	311	NA	0.03	0.02	0.09	0.43	0.07	0.16
Infralittoral mud	0.08	165	NA	0.01	0.01	0.19	0.47	0.14	0.16
Infralittoral sand	0.11	162	NA	0.01	0.01	0.10	0.50	0.08	0.10
Infralittoral mixed sediment	0.07	90	NA	0.01	0.01	0.10	0.27	0.06	0.16

Figure 3

Figure 3. Time series of (a) mean fishing intensity (surface abrasion), (b) proportion of the surface area of the seafloor fished, (c) aggregation of fishing (proportion of the surface area with 90% of the fishing effort) by habitat. Results represent vessels over 15m (2009-2011) and vessels over 12m (2012-2018).

Figure 4

Figure 4. Cumulative proportion of the swept area, landings and value. Grid cells were sorted from highest to lowest fishing intensity and include non-fished cells. The results are for all mobile bottom-contacting gears based on averaged fishing data per c-square from 2013-2018.

Core fishing grounds

Core fishing grounds are defined as the c-squares with the 90% highest value of landings in the VMS data. Figure 5 shows the number of years c-squares are within the 90% highest value by métier. If fishing in a métier occurs in the same c-square every year with high value of landings, the rightmost bar in Figure 5 will be high, meaning that the c-square is within the 90% highest value of landings every year during the period 2013-2018. If a c-square is only within the 90% highest value in one year, it will end up in the bar at the left. Figure 6 shows the percentage area overlap between the 90% highest value per year and the reference fishing ground. Both figures highlight that otter trawling for demersal fish (OT_MIX) dredging for molluscs (DRB_MOL), and seine fishing for demersal fish (SSC_DMF) have the highest variation in space.

Figure 7 illustrates the relationship between area fished in percent and the cumulated value of landings, sorted from the c-squares with highest value fisheries. The curves are start steeply, illustrating the concentration of the fisheries at fishing grounds, and their horizontal component illustrate that peripheral fisheries exist outside the main fishing grounds.

Figure 8 shows the area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018.

Figure 5

Figure 5. Number of years c-squares are within the 90% highest value by métier, presented as a % relative to the total number of c-squares (n) that are within the 90% highest value by métier across all years. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 6

Figure 6. Percentage area overlap between the 90% highest value per year and the reference core fishing ground. For métiers that are included in Figure 5 and missing in Figure 6, no reference core ground could be established and/or métiers were not used in the area in some years.

Figure 7

Figure 7. Percent area fished vs. landings value (euro) by métier, coloured by year. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 8

Figure 8. The area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018. The lightest blue c-squares represent the lowest 10% of total SAR / value of landings. The brown c-squares represent the highest 10% of total SAR / value of landings.

Fishing by métier

Intensity, weight and value of landings are estimated for the grid cells that were fished by one MBCG métier, ignoring cells fished by other métiers (Table 3).

The métier with the highest landings and value per area fished is the otter trawling for small pelagic fish (OT_SPF), but this fishery has a very small footprint. The seines (SDN_DMF and SSC_DMF) have the lowest landings and value per area fished.

Table 3

Table 3. Overview of area fished (sum of swept area), landings and value for the different metiers. Area fished in 1000 km2, weight of landings in 1000 tonnes, value of landings in 10^6 euro.

	DRB_MOL	OT_CRU	OT_DMF	OT_MI	OT_SPF	SDN_DMF	SSC_DMF	TBB_CRU	TBB_DMF	TBB_MOL
Area swept (1000 km2)	1.04	30.43	48.37	0.93	0.01	0.05	3.77	<0.005	<0.005	0
Landings (1000 tonnes)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)	4.20	16.64	22.99	0.87	2.00	0.01	0.84	<0.005	<0.005	0
Landings (1000 tonnes)/Area swept (1000 km2)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)/Area swept (1000 km2)	4.04	0.55	0.48	0.93	213.07	0.23	0.22	1.36	2.49	NA

Impact

No information available

Management scenarios

The figures and tables below show one implementation of multi-purpose habitat management through reductions in effort and spatial closures for the four most extensive MSFD habitat types. They show the unfished area of landings based on a static assessment of effort removal. No impact data is available for this subdivision at present.

The analysis is based on the progressive removal of 5 to 99% of all MBCG fishing effort, starting from the c-squares with the lowest effort (corrected for the areal extent of the MSFD habitat within each c-square). Blue dots show the current situation and are used as reference. The % of unfished area in the reference is only based on grid cells that are unfished.

For all habitats the % unfished drops much faster than the value of the fishery.

MSFD habitat - 1

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	3.86	100.00	NA
5	NA	NA	35.84	94.43	NA
10	NA	NA	45.03	89.73	NA
15	NA	NA	51.32	85.17	NA
20	NA	NA	56.83	80.83	NA
30	NA	NA	66.16	71.90	NA
40	NA	NA	73.46	63.97	NA
60	NA	NA	85.21	46.32	NA
80	NA	NA	93.62	26.20	NA
99	NA	NA	99.87	0.75	NA

MSFD habitat - 2

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	28.28	100.00	NA
5	NA	NA	63.43	90.92	NA
10	NA	NA	71.39	84.61	NA
15	NA	NA	75.63	79.03	NA
20	NA	NA	79.00	73.61	NA
30	NA	NA	84.22	61.32	NA
40	NA	NA	88.06	52.12	NA
60	NA	NA	93.68	34.96	NA
80	NA	NA	97.56	16.35	NA
99	NA	NA	99.92	0.90	NA

MSFD habitat - 3

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	0.17	100.00	NA
5	NA	NA	22.80	92.72	NA
10	NA	NA	32.60	87.42	NA
15	NA	NA	38.74	82.31	NA
20	NA	NA	44.65	76.69	NA
30	NA	NA	55.59	65.38	NA
40	NA	NA	63.84	55.91	NA
60	NA	NA	78.61	38.12	NA
80	NA	NA	91.09	19.99	NA
99	NA	NA	100.00	1.51	NA

MSFD habitat - 4

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	37.25	100.00	NA
5	NA	NA	73.70	90.68	NA
10	NA	NA	83.76	82.39	NA
15	NA	NA	87.81	76.38	NA
20	NA	NA	90.34	70.44	NA
30	NA	NA	92.95	60.95	NA
40	NA	NA	95.01	49.18	NA
60	NA	NA	97.52	35.10	NA
80	NA	NA	99.00	20.31	NA
99	NA	NA	100.00	5.31	NA

Overview all MSFD habitats

Fishing effort consequences, as a % relative to total swept area, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral mud	12.43	<0.1	<0.1	0.7	2.8	7.0	14.1	23.4	35.3	50.7	71.2
Offshore circalittoral sand	24.31	0.0	0.0	0.0	<0.1	0.4	1.4	3.5	8.9	21.9	46.5
Upper bathyal sediment	3.39	0.2	0.7	3.5	8.6	16.4	24.9	35.7	48.7	62.7	79.1
Unknown	31.43	0.0	0.0	0.0	0.0	<0.1	0.6	1.7	3.8	7.6	19.2
Offshore circalittoral coarse sediment	34.97	0.0	0.0	0.0	0.0	0.2	1.1	2.6	5.5	11.2	26.2
Offshore circalittoral mixed sediment	4.09	0.0	0.0	0.0	0.0	<0.1	0.7	1.6	3.4	6.7	27.0
Circalittoral mud	1.26	0.0	0.0	<0.1	1.3	5.1	9.5	17.9	29.9	46.1	67.5
Circalittoral sand	2.78	0.0	0.0	0.0	0.0	0.0	0.5	2.0	5.5	14.0	35.2
Circalittoral coarse sediment	6.6	0.0	0.0	0.0	0.0	0.0	0.7	3.6	7.4	15.7	36.3
Offshore circalittoral rock and biogenic reef	2.93	0.0	0.0	0.0	0.0	0.0	1.0	4.3	10.2	17.6	35.0
Circalittoral rock and biogenic reef	4.08	0.0	0.0	0.0	0.0	0.0	0.0	<0.1	2.4	9.0	21.3
Circalittoral mixed sediment	0.21	0.0	0.0	0.0	0.0	0.8	4.6	15.5	24.7	50.4	60.8
Infralittoral rock and biogenic reef	0.62	0.0	0.0	0.0	0.0	0.0	<0.1	0.6	2.6	8.2	27.5
Upper bathyal sediment or Upper bathyal rock and biogenic reef	0.03	0.1	0.7	2.0	6.9	19.2	40.8	64.8	64.8	100.0	100.0
Infralittoral coarse sediment	0.25	0.0	0.0	0.0	0.0	0.0	0.0	0.4	4.7	16.9	31.7
Infralittoral mud	0.08	0.0	0.0	0.0	0.0	0.0	0.0	0.2	1.8	6.9	48.1
Infralittoral sand	0.11	0.0	0.0	0.0	0.0	0.0	0.0	2.8	6.8	16.4	27.5
Infralittoral mixed sediment	0.07	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	2.4	4.2

Fishing value consequences, as a % relative to total value, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral mud	12.43	<0.1	0.2	1.1	3.5	7.6	14.0	22.4	32.5	45.7	63.8
Offshore circalittoral sand	24.31	0.0	0.0	0.0	<0.1	2.0	3.7	7.3	14.1	30.0	53.3
Upper bathyal sediment	3.39	0.2	2.2	5.6	11.2	19.6	29.1	40.8	52.5	64.4	79.2
Unknown	31.43	0.0	<0.1	<0.1	<0.1	0.2	1.7	3.5	7.8	13.2	29.1
Offshore circalittoral coarse sediment	34.97	0.0	0.0	0.0	0.0	0.3	4.6	7.9	13.2	20.6	40.6
Offshore circalittoral mixed sediment	4.09	0.0	0.0	0.0	0.0	0.3	4.5	5.9	9.4	17.1	37.2
Circalittoral mud	1.26	0.0	0.0	0.2	2.7	7.6	13.6	24.3	37.3	52.8	73.4
Circalittoral sand	2.78	0.0	0.0	0.0	0.0	0.0	1.1	3.6	10.7	23.8	47.8
Circalittoral coarse sediment	6.6	0.0	0.0	0.0	0.0	0.0	0.9	4.1	8.1	18.5	39.4
Offshore circalittoral rock and biogenic reef	2.93	<0.1	<0.1	<0.1	<0.1	<0.1	2.3	7.6	16.7	27.0	54.2
Circalittoral rock and biogenic reef	4.08	0.0	0.0	0.0	0.0	0.0	0.0	<0.1	5.0	16.9	35.7
Circalittoral mixed sediment	0.21	0.0	0.0	0.0	0.0	1.8	8.1	18.9	31.6	58.2	73.7
Infralittoral rock and biogenic reef	0.62	0.0	0.0	0.0	0.0	0.0	<0.1	1.6	7.1	18.9	46.5
Upper bathyal sediment or Upper bathyal rock and biogenic reef	0.03	0.1	0.5	2.1	6.8	19.0	40.7	61.5	61.5	100.0	100.0
Infralittoral coarse sediment	0.25	0.0	0.0	0.0	0.0	0.0	0.0	0.7	6.1	21.7	46.6
Infralittoral mud	0.08	0.0	0.0	0.0	0.0	0.0	0.0	0.6	3.7	15.6	64.0
Infralittoral sand	0.11	0.0	0.0	0.0	0.0	0.0	0.0	3.2	9.2	20.4	38.7
Infralittoral mixed sediment	0.07	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	7.4	8.0

Fishing weight consequences, as a % relative to total weight, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral mud	12.43	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral sand	24.31	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal sediment	3.39	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Unknown	31.43	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral coarse sediment	34.97	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mixed sediment	4.09	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mud	1.26	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral sand	2.78	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral coarse sediment	6.6	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral rock and biogenic reef	2.93	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral rock and biogenic reef	4.08	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mixed sediment	0.21	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral rock and biogenic reef	0.62	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal sediment or Upper bathyal rock and biogenic reef	0.03	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral coarse sediment	0.25	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mud	0.08	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral sand	0.11	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mixed sediment	0.07	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

Southern area

Summary

The physical disturbance pressures from mobile bottom-contacting fishing gears varies spatially in the southern Celtic Seas subdivision, with 95% of the grid cells (I-2), and 79% of the surface area (I-3) being fished on average per year for the period 2013-2018 (Table 1) at depths< 200m, and with 100% of the grid cells (I-2), and 95% of the surface area (I-3) being fished at depths from 200-800m. Fishing is aggregated with 90% of the pressure occurring in 56-72% of grid cells (I-4).

No longevity layer was available for the Northern area subdivision – declines in community biomass relating to impact cannot, therefore, be calculated for either the L1 or PD method.

Maps of spatial distribution of surface abrasion, economic value and weight of fisheries landings are shown in Figure 1. It is evident from the weight map that there is a mistake in the weights for the region, and weights are not presented in further analyses.

Table 1

Table 1. Pressure and impact indicators for 2013-2018

Indicators	0 to 200 m	200 to 800 m	more than 800 m
Average intensity (I-1)	2.60	2.57	NA
Proportion of area in fished cells (I-2)	0.95	1.00	NA
Proportion of area fished per year (I-3)	0.79	0.95	NA
Smallest prop. of area in fished cells with 90% of fishing effort (I-4)	0.56	0.72	NA
Proportion of area in unfished cells (I-5)	0.05	0.00	NA
Average PD impact (I-6)	NA	NA	NA
Average L1 impact (I-6)	NA	NA	NA
Proportion of area with PD impact < 0.2 (I-7)	NA	NA	NA
Proportion of area with L1 impact < 0.2 (I-7)	NA	NA	NA

Figure 1

Figure 1 Geographic distribution of surface abrasion, seabed sensitivity (not shown) and total value and weight from mobile bottom-contacting gear. The maps of surface abrasion, value and weight show the average per year for 2013-2018

Pressure

The distribution of fishing intensity in the Southern area subdivision is relatively evenly distributed (Figure 2), with a higher concentration of fishing effort occurring to the south of St George’s Channel.

The proportion of the area subject to fishing pressure differs between broad-scale habitats and is highest in offshore circalittoral mud (100% of grid cells fished) and offshore circalittoral sand (100% of grid cells fished) (Table 2). Fishing intensity is highest in Offshore circalittoral coarse sediment (average intensity = 3.18 year-1), offshore circalittoral mud (average intensity = 3.98 year-1) and offshore circalittoral sand (average intensity = 2.29 year-1) and some other much smaller habitats.

Total fishing intensity remained unchanged over time from 2016 - 2018 (Figure 3). This overlay larger variations within the individual habitat classifications, the most consistent across the habitat classes being a decline in 2010. Average trawling intensity is more variable over time than the proportion of area fished (Figure 3, compare left and middle panel), with the exception of a strong, single-year reduction in most seafloor categories in 2010 which is also evident in total fishing intensity. Taken over the 10 year reporting period, this comparison shows that changes in intensity have not affected greatly the spatial distribution of the footprint.

Fishing pressure is aggregated at the level of the habitat (Figure 3, right panel). In all but abyssal areas, which are subject to a very small fishing footprint, the smallest proportion of habitat with 90% of effort varies between 35-65%. Please note that this lower 35% is driven by the category ‘unknown’. The intensively fished areas represent the ‘core fishing grounds’. These grounds contribute most of the landings and value (Figure 4). Approximately 55% of the fishing effort (swept area) and 50% of the landings and value, occur in only 20% of the surface area of the Northern area subdivision (Figure 4).

Figure 2

Figure 2 Surface abrasion, Swept Area Ratio, by mobile bottom-contacting gears (year-1), averaged for the 2013-2018 six-year cycle

Table 2

Table 2 Overview of pressure indicators of all mobile bottom-contacting gears per broad-scale habitat averaged for 2013-2018. I refers to the indicators in Table 1.

MSFD broad habitat type	Extent of habitat (1000 km2)	Number of grid cells	Landings 1000 tonnes	Value 106 euro	Swept area 1000 km2	Average intensity (I-1)	Prop. of area in fished grid cells (I-2)	Prop. of area fished per year (I-3)	Smallest prop. of area with 90% of fishing effort (I-4)
Offshore circalittoral coarse sediment	67.08	4543	NA	94.99	213.60	3.18	0.99	0.85	0.47
Offshore circalittoral sand	74.50	5312	NA	57.32	170.62	2.29	1.00	0.88	0.55
Offshore circalittoral mud	36.17	2564	NA	51.30	144.01	3.98	1.00	0.96	0.52
Unknown	7.79	1174	NA	3.29	12.16	1.56	0.92	0.76	0.27
Offshore circalittoral mixed sediment	1.45	323	NA	2.56	5.98	4.12	0.97	0.88	0.33
Upper bathyal sediment	1.13	150	NA	1.24	3.80	3.38	1.00	0.99	0.44
Circalittoral coarse sediment	7.36	982	NA	4.39	3.73	0.51	0.86	0.26	0.19
Upper bathyal sediment or Upper bathyal rock and biogenic reef	1.29	130	NA	0.93	3.16	2.45	1.00	0.89	0.58
Offshore circalittoral rock and biogenic reef	2.51	876	NA	0.97	2.65	1.06	0.96	0.55	0.31
Circalittoral sand	3.54	686	NA	0.91	1.88	0.53	0.74	0.29	0.17
Infralittoral sand	0.91	362	NA	1.39	1.18	1.31	0.63	0.39	0.06
Circalittoral rock and biogenic reef	3.05	1017	NA	0.38	0.71	0.23	0.67	0.17	0.21
Infralittoral coarse sediment	0.47	292	NA	1.51	0.60	1.27	0.85	0.38	0.08
Circalittoral mud	0.52	233	NA	0.12	0.32	0.62	0.64	0.32	0.14
Infralittoral rock and biogenic reef	0.58	534	NA	0.23	0.07	0.13	0.65	0.09	0.12
Circalittoral mixed sediment	0.19	93	NA	0.02	0.07	0.35	0.74	0.32	0.23
Infralittoral mud	0.11	101	NA	0.01	0.01	0.08	0.10	0.05	0.04
Upper bathyal rock and biogenic reef	0.01	10	NA	0.00	0.01	1.31	1.00	0.70	0.30
Infralittoral mixed sediment	0.02	31	NA	0.00	0.00	0.01	0.06	0.01	0.03

Figure 3

Figure 3. Time series of (a) mean fishing intensity (surface abrasion), (b) proportion of the surface area of the seafloor fished, (c) aggregation of fishing (proportion of the surface area with 90% of the fishing effort) by habitat. Results represent vessels over 15m (2009-2011) and vessels over 12m (2012-2018).

Figure 4

Figure 4. Cumulative proportion of the swept area, landings and value. Grid cells were sorted from highest to lowest fishing intensity and include non-fished cells. The results are for all mobile bottom-contacting gears based on averaged fishing data per c-square from 2013-2018.

Core fishing grounds

Core fishing grounds are defined as the c-squares with the 90% highest value of landings in the VMS data. Figure 5 shows the number of years c-squares are within the 90% highest value by métier. If fishing in a métier occurs in the same c-square every year with high value of landings, the rightmost bar in Figure 5 will be high, meaning that the c-square is within the 90% highest value of landings every year during the period 2013-2018. If a c-square is only within the 90% highest value in one year, it will end up in the bar at the left. Figure 6 shows the percentage area overlap between the 90% highest value per year and the reference fishing ground. Both figures highlight that otter trawling for demersal fish (OT_MIX) dredging for molluscs (DRB_MOL), and seine fishing (SSC_DMF, SDN_DMF) have the highest variation in space.

Figure 7 illustrates the relationship between area fished in percent and the cumulated value of landings, sorted from the c-squares with highest value fisheries. The curves are start steeply, illustrating the concentration of the fisheries at fishing grounds, and their horizontal component illustrate that peripheral fisheries exist outside the main fishing grounds.

Figure 8 shows the area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018.

Figure 5

Figure 5. Number of years c-squares are within the 90% highest value by métier, presented as a % relative to the total number of c-squares (n) that are within the 90% highest value by métier across all years. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 6

Figure 6. Percentage area overlap between the 90% highest value per year and the reference core fishing ground. For métiers that are included in Figure 5 and missing in Figure 6, no reference core ground could be established and/or métiers were not used in the area in some years.

Figure 7

Figure 7. Percent area fished vs. landings value (euro) by métier, coloured by year. The outcome is only shown for métiers that have >50 uniquely fished c-squares in the period 2013-2018.

Figure 8

Figure 8. The area associated with each 10-percentile interval for each métier using averages of SAR (left column) and landings value (euro, right column) for the period 2013-2018. The lightest blue c-squares represent the lowest 10% of total SAR / value of landings. The brown c-squares represent the highest 10% of total SAR / value of landings.

Fishing by métier

Intensity, weight and value of landings are estimated for the grid cells that were fished by one MBCG métier, ignoring cells fished by other métiers (Table 3).

The métier with the highest landings and value per area fished is the beam trawling for molluscs (TBB_MOL). Note this is driven by a very small area. The seines (SDN_DMF and SSC_DMF) have the lowest landings and value per area fished.

Table 3

Table 3. Overview of area fished (sum of swept area), landings and value for the different metiers. Area fished in 1000 km2, weight of landings in 1000 tonnes, value of landings in 10^6 euro.

	DRB_MOL	OT_CRU	OT_DMF	OT_MI	OT_SPF	SDN_DMF	SSC_DMF	TBB_CRU	TBB_DMF	TBB_MOL
Area swept (1000 km2)	2.98	45.03	436.42	11.46	0.17	5.85	46.20	<0.005	20.60	<0.005
Landings (1000 tonnes)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)	11.79	24.50	135.10	8.83	0.34	0.78	6.65	<0.005	34.88	<0.005
Landings (1000 tonnes)/Area swept (1000 km2)	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Value (10^6 euro)/Area swept (1000 km2)	3.96	0.54	0.31	0.77	2.01	0.13	0.14	0.36	1.69	10.59

Impact

No information available

Management scenarios

The figures and tables below show one implementation of multi-purpose habitat management through reductions in effort and spatial closures for the four most extensive MSFD habitat types. They show the unfished area of landings based on a static assessment of effort removal. No impact data is available for this subdivision at present.

The analysis is based on the progressive removal of 5 to 99% of all MBCG fishing effort, starting from the c-squares with the lowest effort (corrected for the areal extent of the MSFD habitat within each c-square). Blue dots show the current situation and are used as reference. The % of unfished area in the reference is only based on grid cells that are unfished.

For all habitats the % unfished drops much faster than the value of the fishery.

MSFD habitat - 1

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	1.49	100.00	NA
5	NA	NA	27.30	94.41	NA
10	NA	NA	37.53	88.93	NA
15	NA	NA	45.13	83.17	NA
20	NA	NA	51.55	77.34	NA
30	NA	NA	62.21	65.56	NA
40	NA	NA	70.85	55.41	NA
60	NA	NA	84.46	34.96	NA
80	NA	NA	93.99	16.96	NA
99	NA	NA	99.80	0.91	NA

MSFD habitat - 2

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	0.18	100.00	NA
5	NA	NA	19.65	93.02	NA
10	NA	NA	30.66	86.32	NA
15	NA	NA	39.39	80.49	NA
20	NA	NA	46.87	75.11	NA
30	NA	NA	59.44	65.00	NA
40	NA	NA	69.45	54.99	NA
60	NA	NA	84.61	35.07	NA
80	NA	NA	94.78	16.20	NA
99	NA	NA	99.93	0.54	NA

MSFD habitat - 3

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	0.02	100.00	NA
5	NA	NA	20.04	95.28	NA
10	NA	NA	33.56	90.74	NA
15	NA	NA	44.04	86.58	NA
20	NA	NA	52.18	82.75	NA
30	NA	NA	65.15	74.39	NA
40	NA	NA	74.74	65.43	NA
60	NA	NA	88.49	46.77	NA
80	NA	NA	96.36	26.19	NA
99	NA	NA	99.89	1.66	NA

MSFD habitat - 4

Multi-purpose habitat management trade-off for the most extensive MSFD habitat type.

Table presenting a similar overview as above, while including weight of landings

Effort reduction (%)	Average PD impact	Average L1 impact	Area unfished (%)	Value (%)	Weight (%)
0	NA	NA	7.57	100.00	NA
5	NA	NA	28.42	93.86	NA
10	NA	NA	35.42	88.72	NA
15	NA	NA	40.95	84.00	NA
20	NA	NA	46.33	79.28	NA
30	NA	NA	55.85	69.82	NA
40	NA	NA	65.10	60.32	NA
60	NA	NA	80.50	40.92	NA
80	NA	NA	92.28	20.98	NA
99	NA	NA	100.00	0.82	NA

Overview all MSFD habitats

Fishing effort consequences, as a % relative to total swept area, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral coarse sediment	67.08	<0.1	0.6	2.6	6.1	11.6	18.8	27.8	38.9	52.7	70.8
Offshore circalittoral sand	74.5	0.5	1.7	5.2	9.7	15.4	22.3	30.5	40.7	53.3	69.6
Offshore circalittoral mud	36.17	1.0	2.2	5.0	8.5	13.0	18.6	25.8	34.8	46.6	63.1
Unknown	7.79	0.0	<0.1	1.5	6.0	14.1	23.4	34.5	46.1	59.7	75.7
Offshore circalittoral mixed sediment	1.45	0.1	1.3	4.0	7.7	12.8	18.1	26.4	35.4	50.3	76.2
Upper bathyal sediment	1.13	2.7	5.3	13.2	21.0	28.4	36.4	43.1	53.4	67.1	82.6
Circalittoral coarse sediment	7.36	0.0	0.0	<0.1	0.7	2.0	4.0	7.3	12.1	20.6	35.3
Upper bathyal sediment or Upper bathyal rock and biogenic reef	1.29	0.7	2.1	6.1	13.2	21.5	30.2	42.7	54.0	66.6	83.5
Offshore circalittoral rock and biogenic reef	2.51	<0.1	0.5	3.6	7.5	12.4	19.3	26.0	37.7	49.9	65.6
Circalittoral sand	3.54	0.0	0.0	0.0	0.1	1.0	2.7	7.6	16.6	26.0	45.6
Infralittoral sand	0.91	0.0	0.0	0.0	0.0	<0.1	0.2	2.2	10.0	29.7	52.8
Circalittoral rock and biogenic reef	3.05	0.0	0.0	0.0	0.0	0.4	2.1	6.2	15.6	26.2	46.4
Infralittoral coarse sediment	0.47	0.0	0.0	<0.1	0.2	1.1	2.8	5.8	11.6	21.8	62.9
Circalittoral mud	0.52	0.0	0.0	0.0	0.0	0.1	2.2	6.9	12.9	25.7	45.6
Infralittoral rock and biogenic reef	0.58	0.0	0.0	0.0	0.0	<0.1	0.7	1.9	4.6	13.9	28.0
Circalittoral mixed sediment	0.19	0.0	0.0	0.0	<0.1	0.7	7.6	18.8	30.8	63.8	80.9
Infralittoral mud	0.11	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Upper bathyal rock and biogenic reef	0.01	1.3	1.3	1.3	1.3	38.1	38.1	38.1	68.3	68.3	100.0
Infralittoral mixed sediment	0.02	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Fishing value consequences, as a % relative to total value, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral coarse sediment	67.08	0.1	0.6	2.9	6.9	12.7	21.2	32.0	43.6	57.7	75.1
Offshore circalittoral sand	74.5	0.8	2.4	7.2	13.4	19.9	27.3	35.5	45.7	58.5	74.0
Offshore circalittoral mud	36.17	1.2	2.4	4.7	8.0	11.9	16.3	22.0	30.0	40.9	56.1
Unknown	7.79	0.0	<0.1	2.0	7.4	15.1	23.9	34.3	45.7	59.1	74.6
Offshore circalittoral mixed sediment	1.45	0.3	1.7	5.3	9.5	15.0	20.1	28.9	39.4	55.1	77.9
Upper bathyal sediment	1.13	2.6	5.3	13.1	21.6	29.4	38.6	44.7	54.8	68.2	83.6
Circalittoral coarse sediment	7.36	0.0	0.0	0.2	1.6	3.6	5.9	11.3	15.7	27.9	46.0
Upper bathyal sediment or Upper bathyal rock and biogenic reef	1.29	0.8	1.8	6.2	14.2	22.0	31.4	45.0	54.8	67.3	82.9
Offshore circalittoral rock and biogenic reef	2.51	<0.1	0.7	4.9	9.2	14.3	21.8	27.8	40.4	52.2	66.3
Circalittoral sand	3.54	0.0	0.0	0.0	0.6	4.3	8.0	15.1	26.7	33.4	53.7
Infralittoral sand	0.91	0.0	0.0	0.0	0.0	<0.1	0.9	8.7	19.3	38.4	58.7
Circalittoral rock and biogenic reef	3.05	0.0	0.0	0.0	0.0	2.3	8.7	19.7	32.7	51.2	68.6
Infralittoral coarse sediment	0.47	0.0	0.0	0.1	1.1	2.9	8.6	11.7	24.5	43.3	68.7
Circalittoral mud	0.52	0.0	0.0	0.0	0.0	0.2	5.6	18.3	22.6	37.8	50.9
Infralittoral rock and biogenic reef	0.58	0.0	0.0	0.0	0.0	<0.1	1.1	4.1	10.0	19.6	35.4
Circalittoral mixed sediment	0.19	0.0	0.0	0.0	0.3	1.3	7.6	10.8	18.0	52.1	78.8
Infralittoral mud	0.11	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0
Upper bathyal rock and biogenic reef	0.01	1.4	1.4	1.4	1.4	36.5	36.5	36.5	69.5	69.5	100.0
Infralittoral mixed sediment	0.02	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0	0.0

Fishing weight consequences, as a % relative to total weight, of protecting a certain fraction of each broad habitat type sorted from low to high fished c-squares

MSFD broad habitat type	Extent of habitat 1000 km2	0.05	0.1	0.2	0.3	0.4	0.5	0.6	0.7	0.8	0.9
Offshore circalittoral coarse sediment	67.08	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral sand	74.5	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mud	36.17	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Unknown	7.79	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral mixed sediment	1.45	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal sediment	1.13	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral coarse sediment	7.36	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal sediment or Upper bathyal rock and biogenic reef	1.29	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Offshore circalittoral rock and biogenic reef	2.51	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral sand	3.54	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral sand	0.91	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral rock and biogenic reef	3.05	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral coarse sediment	0.47	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mud	0.52	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral rock and biogenic reef	0.58	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Circalittoral mixed sediment	0.19	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mud	0.11	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Upper bathyal rock and biogenic reef	0.01	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA
Infralittoral mixed sediment	0.02	NA	NA	NA	NA	NA	NA	NA	NA	NA	NA

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WKTRADE3 developed an assessment of fishing footprint of mobile bottom-contacting fishing gears (MBCG) and benthic impact that is appropriate for a six-year management cycle of MSFD assessments. The assessment maps and pressure and impact indicator values produced are based on an average fishing intensity of 2013-2018. This assessment period is linked to the latest available fishing data, rather than to the MSFD Art 8 assessment periods. The assessment product further shows year-to-year variation in pressure and impact from 2009.

The assessment presents five pressure indicators and two benthic impact indicators by (sub-)regional, subdivision sea, or broadscale habitat type within that sea (Table 1), following ICES 2017 advice. The assessment further describes spatial and temporal variation of core MBCG fishing footprints. Lastly, the assessment describes a trade-off analysis between fisheries and the seafloor based on a management scenario where fishing effort is reduced through spatial closures in each broadscale habitat type.

Table 1. Pressure and impact indicators that are applied by (sub-)regional, subdivision sea, or broadscale habitat type within that sea at a 0.05° × 0.05° grid, hereafter termed c-square.

Indicators	Description
Intensity (I-1)	Average number of times the area is swept per year by MBCG. Estimated as the sum of swept area for all MBCG (averaged for the six-year cycle), divided by the total area.
Proportion of grid cells fished (I-2)	The number of c-squares fished at least once in the six-year cycle (irrespective of the swept area within the cell), divided by the total number of c-squares.
Proportion of area fished (I-3)	The sum of swept area across all c-squares based on the average for the six-year cycle, where swept area in a specific grid cell cannot be greater than the area of that grid cell, divided by the summed area of all c-squares.
Aggregation of fishing pressure (I-4)	The smallest proportion of c-squares in the area where 90% of the total swept area occurs.
Persistently unfished areas (I-5)	The number of c-squares persistently unfished in the six-year cylce (irrespective of the swept area within the cell), divided by the total number of c-squares.
Impact (I-6)	Average fishing impact across c-squares (averaged for the six-year cycle).
Proportion area with impact <0.2 (I-7)	The proportion of c-squares with an average impact below 0.2 (averaged for the six-year cycle)

Data limitations in Celtic Seas sub-region

Weight of landings data for OT_DMF is unrealistically high and likely based on erroneous inputs (red area in Figure 1 - weight of landings). The drop in trawling intensity in 2017 in some habitats/areas is (most likely) a data artefact. No longevity data available to estimate benthic impact.

Temporal patterns in fishing activity are available from 2009 for vessels over 15m and from 2012 for vessels over 12m. Temporal variation in fishing activity hence represents vessels over 15m (2009-2011) and vessels over 12m (2012-2018). The assessment maps and indicator values produced are based on an average for 2013-2018.

How are changes in the fishing footprint analyzed?

To describe the fishing footprint, we expressed fishing intensity as swept-area ratios (SAR). The swept area is calculated as hours fished x average fishing speed x gear width. The gear width is estimated based on relationships between average gear widths and average vessel length or engine power (kW), as stated in Eigaard et al. (2016) and using ICES expert input. The swept-area ratio is the sum of the swept area divided by the area of each grid cell (c-square). Therefore, the C-square SAR value indicates the theoretical number of times the entire grid cell has been swept if effort was evenly distributed within the cell. For example, a SAR of 2 means that each location within the c-square is fished 2 times over the year, a SAR of 0.5 means that each location within the c-square is fished once in two years. Due to data availability, all analyses of the fishing footprint do not account for sub-grid variation of fishing events within the c-square.

In order to better understand the relationship between catch/value of landings and the levels of physical disturbance for MSFD purposes, the analysis considers ten gear groupings (hereafter termed métiers) together with the total intensity of all gears (Table 2).

Table 2 Gear groupings used in the analysis. Note that OT_CRU includes OT_MIX_CRU and OT_MIX_CRU_DMF, and, OT_MIX includes OT_MIX_DMF_BEN and OT_MIX_DMF_PEL.

Métier	Main gear type	Target species assemblage group	Main target species	Depletion rate
DRB_MOL	Dredge	Molluscs	Scallops	0.200
OT_CRU	Otter trawl	Crustaceans	Nephrops, Pandalus, mixed fish	0.100
OT_DMF	Otter trawl	Demersal fish	Cod or plaice	0.026
OT_MIX	Otter trawl	Mixed fish	Mixed fish	0.074
OT_SPF	Otter trawl	Small pelagic fish	Sprat or sandeel	0.009
SDN_DMF	Danish seine	Demersal fish	Plaice, cod	0.009
SSC_DMF	Flyshooter (seine)	Demersal fish	Cod, haddock, flatfish	0.016
TBB_CRU	Beam trawl	Crustaceans	Brown shrimp	0.060
TBB_DMF	Beam trawl	Demersal fish	Flatfish	0.140
TBB_MOL	Beam trawl	Molluscs	Whelk, snails and scallops	0.060

How is benthic impact evaluated?

No prediction of benthic community longevity is available and no benthic impact is estimated.

References

Eigaard O.R., Bastardie F., Breen M.l., Dinesen G.E., Lafargue P., Nielsen J.R., Nilson H., O’Neil F., Polet H., Reid D., Sala A., Sköld M., Smith C., Sørensen T.K., Tully O., Zengin M., Hintzen N.T., Rijnsdorp A.D. (2016). Estimating seafloor pressure from trawls and dredges based on gear design and dimensions. ICES J. Mar. Sci. 73(1): 27-43 https://doi.org/10.1093/icesjms/fsv099

ICES 2017. EU request on indicators of the pressure and impact of bottom-contacting fishing gear on the seabed, and of trade-offs in the catch and the value of landings. ICES Special Request Advice, eu.2017.13. 27 pp. https://doi.org/10.17895/ices.advice.5657.